THEADVANCED

OFFICEASSISTANT

MODULE 3

2

Index1. Lenses, Lens materials and

Coatings

2. Understanding Prescription

3. Measurements

4. Using a Vertometer

5. Adjusting a Frame

6. Contact Lens(Lens types and Dispensing)

7. Stock Lens Management (Ophthalmic and Contact Lenses)

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1. LENSES, LENS MATERIALS AND COATINGS

LENS TYPES

Single Vision LensesThe simplest form of spectacle or contact lens is the single-vision lens, made to a

single prescription to correct a particular eyesight problem. Concave lenses are

used to correct short sight and convex lenses to correct long sight. A concave

lens is generally thinner in the centre than at the edge and a convex lens is

usually thinner at the edge than in the centre. The curvature of the lens, its

thickness and weight will depend on the amount of long or short sight it is

designed to correct. The lens material will also influence the thickness and

weight of your lenses, as will the size and shape of the spectacle frame you

choose. Traditionally, spectacle lenses were made of glass but most lenses are

now lightweight plastic and there is a wide range of materials available to suit

your prescription and lifestyle.

Single vision lenses have the same optical power throughout the lens.

Depending on the patient's prescriptions these lenses may be appropriate for full

or part-time use at distance only, near only, or both distance and near.

When patients develop presbyopia, they need a different optical power to see

clearly at distance and near. Depending on the distance they are conducting

their near visual tasks, different optical powers may be needed (e.g., one pair of

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spectacles may be needed to read a book, and another pair may be needed to

see the computer or desktop which is at a farther distance).

Fitting Tips:

Ensure that the pupillary distance is spot on.

Use High Refractive Index in high scripts to ensure comfort and the best

cosmetic affect.

BIFOCALS AND TRIFOCALS

Bifocal lenses contain two optical corrections with a distinct dividing line between

the two parts. The most common use of bifocals is for people who have become

presbyopic and need a different prescription for close work. The upper part of the

lens corrects distance vision and the lower half is for near vision. Trifocals are

also available that have three sections and incorporate a correction for

intermediate vision. Bifocals and trifocals come in a range of designs but

nowadays varifocal lenses are much more likely to be prescribed.

General Considerations - Bifocal:

Upper portion conveys distance – lower window conveys near.

Segment width available in 28mm or 35mm (25mm being phased out).

Movement from distance to near will cause “image-jump”

Not all segment widths are available in all materials.

Distance

Near

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Fitting Tips - Bifocal:

Generally this lens is fitted on the lower eye lid.

Easy adaptation – most common complaint being intrusion of the eye.

Affords good usability to scan with wide field.

Minimum seg height: adults = 15 mm

children = 12 mm

TRIFOCALS

General Considerations and lens information

Upper portion conveys distance, lower window conveys near and middle

window conveys intermediate vision.

Segment width available in 28mm and 35mm (25mm being phased out).

Power of intermediate window is usually 50% that of the reading add power.

This lens allows good scanning and wide field for the advanced

presbyope.

Fitting Tips

Generally this lens is fitted at the lower pupil

Easy adaptation. Most common complaint is intrusion of the line. Affords

good usability over a wide field

Used for higher presbyopes that need more help with range

Distance

Intermediate

Near

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PROGRESSIVES (INVISIBLE OR NO-LINE BIFOCALS)

Modern technology has allowed the development of ever-more advanced

progressive lenses with easier adaptation. They are designed to be the most

similar to "natural" vision possible. In a progressive lens, the distance power is

located in the top part of the lens and the near section is located in the lower part

of the lens. One of the main functional advantages of this type of lens is that

there is also a "progression" of optical power throughout the lens from the

distance section to the near section which can be used for various intermediate

(in-between distance) visual tasks. Improved cosmetic appearance is a definite

advantage since no lines are visible; it is for this reason they are also called

invisible or no-line bifocals. Because there is some adaptation and there are

some limitations with the use of these lenses, proper fitting, adjustment, and

instruction on their proper use is particularly important.

Distance range The large distance zone of our progressive lenses will meet all your requirements

for razor-sharp vision without compromise. Even when you move your eyes

continually between various distances, you will see your surroundings clearly and

precisely. You will even recognize all details on the distant horizon comfortably.

Middle distance range Progressive lenses also provide you with comfortable, clear vision in the range

between far and near.

Distance

Intermediate

Near

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Near range The near zone of our progressive lenses has been adapted to the natural

lowering of the eyes when reading. This means that you can read comfortably

without any contortions of your head or body.

Other Specialty Multifocal Occupational LensesIf you were to look at a near object located above your head with normal

multifocal lenses it would appear blurry, since no near add would be present.

Single vision eyeglasses for near can be used to accomplish these tasks.

However, they cannot be worn continuously since they cause blurry vision at

distance. Occupational bifocals and trifocals are available for this specialized

task.

Computer Lenses for Presbyopia (Office Lens)Ophthalmic companies

have developed task-

specific lenses which

have been designed for

computer/reading use

only. These lenses are

similar to a progressive

lens with the near

section located in the

lower part of the lens, but

the top part of the lens

contains an intermediate distance optical power for computer use (these lenses

are blurry for distant objects). Although for most patients progressives lenses

work very well at the computer, these task-specific lenses offer larger optical

areas for intermediate and near tasks such as working on the computer and

reading.

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LENS MATERIALS

TRADITIONAL GLASS Glass was the first lens material used to make modern-day eyeglasses. Its

earliest use is documented back to the 13th century in Venice, Italy. It remained

the only lens material choice for almost 600 years until the introduction of plastic

lens materials in the mid 1900's.

Glass lenses have excellent optical qualities and can have a refractive index as

high as 1.90. But safety standards require a lens center thickness of 2.0 mm for

glass as compared to half that thickness or 1.0 mm center thickness for 1.60 or

1.66 high index plastic. This requirement is why glass lenses need to be thicker

than newer lens materials like high index plastic. Glass lenses are heavy and

uncomfortable to wear. Stronger lens prescriptions give the unsightly "coke

bottle" or "bug eye" look to the lens wearer.

Pros of Glass

doesn't scratch as easily as plastic

has excellent optical qualities

Cons of Glass

heavy to wear

uncomfortable, constantly slides down the nose

strong minus prescriptions have unsightly edges giving the notorious "coke

bottle" effect or the typical "bug eye" look of high plus prescriptions

poor impact resistance as compared to high index plastic and polycarbonate

CONVENTIONAL PLASTIC (CR39) Conventional or ordinary plastic, introduced in the late 1960's, was the first

lightweight plastic lens and provided improved lens comfort as compared to glass

lenses. Conventional plastic lenses still have the same unsightly thick edges as

glass, but it has good optical qualities. It also provides more impact resistance

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than glass, but has less resistance than newer lens materials like polycarbonate

and polyurethane high index plastic. It does not have the dramatic cosmetic

advantages of newer high index lens materials that combine lightweight with

thinness.

Pros of Conventional Plasticlighter and more comfortable than glass

more impact resistant than glass

good optical qualities

Cons of Conventional Plasticeasier to scratch than glass

same unsightly thick edges as glass

has less impact resistance than polycarbonate, 1.60 or 1.66 high index

plastic

HIGH REFRACTIVE INDEX LENSES The refractive index of a lens material - its ability to bend light - plays a critical

role in the creation of the power and thickness of a lens. For any lens design, the

higher the index, the flatter the front and back curvature of the lens surface

needed for a given optical power. As a result of these flatter curves, the thickness

of the lens is automatically reduced. The figure below shows how the curvature

of the front and back surfaces for -6.00 D and +4.00 D spherical lenses with a 1.6

high index plastic are clearly flatter than the curvatures produced with 1.5 index

CR-39.

Comparative thickness of CR-39 lenses and 1.6 High Index

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Furthermore, the nature of high-index plastic makes it possible to grind minus-

power lenses to a thinner center thickness than CR-39 while keeping the lens'

impact-resistant properties. High-index plastic materials may be ground to a 1.5

mm center thickness in the minus range and still satisfy impact-resistance

standards, while CR-39 is generally ground to 2.0 mm in the minus range to

respect these standards.

High-index plastic is used to significantly reduce lens thickness. For example, a

1.6 High Index Plastic has a refractive index of 1.595. A simple calculation shows

that, compared with CR-39, materials with a 1.595 high-index will reduce edge

thickness for a spherical -6.00 D / 70-mm diameter lens by 2.1 mm or 20 percent

(including 0.5 mm offered by thinner surfacing), and center thickness for a +4.00

D / 70-mm diameter lens by almost 1.0 mm or 16 percent.

High index plastic, though an efficient tool for thinner lenses in its own right,

works best when combined with optimal frame selection. The thinnest lens is

always obtained with the smallest and roundest eye-sized frame with a frame PD

as close as possible to the wearer's binocular PD in order to minimize lens

decentration. For plus prescriptions, the thinnest lens is always obtained with an

optimized minimum edge thickness, remembering that a rimless frame imposes

greater edge thickness. By combining these basic dispensing rules with the

properties of a true 1.6 high index plastic material, we can ensure that our

patients enjoy the advantages of very thin, light, and comfortable lenses.

However, we also want to draw your attention to the fact that high and medium

index plastic lenses are less scratch resistant than CR-39 and need a scratch

resistant coating on both their front and back surfaces. Some manufacturers,

deliver blanks with a front surface scratch-resistant coating and recommend a

back-side scratch-resistant coating for all high-index plastic. High and medium

index plastic lenses are less scratch resistant than CR-39 and generally need a

scratch-resistant coating on both their front and back surfaces.

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The laws of physics hold that, in general, the higher the refractive index of a

material, the greater its tendency to disperse light and create rainbow contours of

objects seen through a lens periphery. This chromatic dispersion exists in any

lens, but is slightly more pronounced in high-index materials. However, it never

occurs in the central part of a lens and can only be noticed in the periphery of

extremely high-powered lenses made in very dispersive materials because a

strong prismatic effect must be present for it to be noticeable. The dispersive

power of a lens material is characterized by its abbe value.

1.6 HIGH INDEX PLASTIC In 1987 the first 1.60 high index plastic lens was introduced. Experts combined

the three most sought-after lens benefits -- lightweight, thinness, and truly

distortion-free optics into one lens product. Not only was the lens lightweight and

ultra thin, it also delivered an unique level of optical quality. The lens dramatically

improved the cosmetic appearance of the eyes and glasses, and eliminated

many common eyeglass complaints --the rainbow swim effect (associated with

polycarbonate), peripheral distortion, magnification and minification of objects, or

the "bug eyes" or "coke bottle eyes" look.

For the first time, spectacle wearers could wear thinner and lighter lenses without

giving up optical quality which was so lacking in polycarbonate lenses and could

wear lenses that were lighter than conventional or regular plastic (CR-39), had

dramatically thinner edges, and had superior optical qualities. The 1.60 lens was

the thinnest, lightest, and most optically superior lens until the "next generation"

of high index lenses, the 1.66 high index lenses were introduced in 1992, and the

1.66 progressive (no line bifocal) in 1995.

Pros of 1.60 High Index Plastic Lenses

superior optical qualities

thinner computer-designed lenses eliminate distortion

greatly enhanced cosmetic appearance

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lighter weight for unsurpassed comfort

better scratch resistance than polycarbonate

impact resistance is five times that of conventional plastic or glass

Cons of 1.60 High Index Plastic Lenses

not as thin or as light as the "next generation" 1.66 high index lenses

easier to scratch than glass

slightly higher cost than polycarbonates

impact resistance is slightly less than polycarbonate

1.66 HIGH INDEX PLASTIC In 1992 the first 1.66 high index plastic lens was introduced representing the

"Next Generation" of high index lenses. These lenses combine the benefits of

ultra thin and ultra light lenses with superior optics. Computer-engineered

aspheric lens designs eliminate peripheral distortion. An incredible 50,000 points

on a lens are computer calculated and connected for smooth transitions

throughout the entire lens surface. The optical qualities of 1.60, and the new

thinner and lighter 1.66 high index plastic lenses far exceed the optical qualities

of earlier plastic lens materials. These lenses

are available in 1.66 high index single vision

lenses as well as a 1.66 progressive lens.

They are up to 27% thinner and lighter than

the previous standard, 1.60 lenses and up to

50% thinner and lighter than conventional or

ordinary plastic lenses.

Pros of 1.66 High Index Plastic Lenses

superior optical qualities

thinner computer-designed lenses eliminate distortion

greatly enhanced cosmetic appearance

lighter weight for unsurpassed comfort

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better scratch resistance than polycarbonate

impact resistance is five times that of conventional plastic or glass

Cons of 1.66 High Index Plastic Lenses

easier to scratch than glass

slightly higher cost than polycarbonate

impact resistance is slightly less than polycarbonate

HIGH REFRACTIVE INDEX 1.70, 1.80 & 1.90 The refractive index of the material is a general guide to how thin the lens will be.

From ordinary 1.5 index lenses there are 1.55, 1.6, 1.7, 1,8 and 1.9 materials -

each step up makes the lens about 20% thinner than the previous index.

Pros

Thinner and lighter than glass and plastic

Better optical quality than polycarbonate

Cons

Susceptible to scratching (correctable by

coating)

Susceptible to backside and inner-

surface reflections (correctable with AR)

ASPHERIC LENSES The term “aspheric” relates to the 'shape' of a lens surface - rather than being

manufactured with a simple 'spherical curve' the lens has a complex series of

curves which are designed to reduce distortion and lens thickness. Often used

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with High Index materials they provide clearer peripheral vision, especially for

more powerful prescriptions.

POLYCARBONATE LENSES Polycarbonate plastic was the original high index lens material and was

introduced in 1983. It provided the ability to make thinner and lighter lenses. It

has great impact resistance, but poor optical qualities as compared to newer

technological breakthroughs, such as high index polyurethane plastic 1.60 and

1.66 lenses. Polycarbonate is often prescribed for lens wearers in high-risk

professions such as policemen and firemen where the risk of eye injury

outweighs the optical disadvantages.

Pros of Polycarbonate Lenses

high impact resistance

thinner and lighter than conventional (ordinary) plastic or glass

Cons of Polycarbonate Lenses

poor optical qualities

more lens distortion than glass, conventional plastic, and high index plastic

less scratch resistance than other high index plastics

Lens Type Summary

Lens Type Refractive Index Light Transmission % UV cut off (nm)

Crown Glass 1.523 91.6 280 - 310 Hi-Index 1.6 89.6 330 Hi-Index 1.7 87 330 Hi-Index 1.8 84.3 330 Hi-Index 1.9 81.6 Plastic CR39 1.49 92.3 350 Plastic CR39 1.56 90.6 365 Polycarbonate 1.586 90 370 Hi-Index 1.6 89.6 380 Hi-Index 1.67 87.8 380

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TINTING AND COATING The color of the tint determines the parts of the light spectrum that are absorbed

by the lenses. Manufacturers use different colors to produce specific results.

Gray tints are great all-purpose tints that reduce the overall amount of

brightness with the least amount of color distortion. Gray lenses offer good

protection against glare, making them a good choice for driving and general

use.

Yellow or gold tints reduce the amount of blue light while allowing a larger

percentage of other frequencies through. Since blue light tends to bounce

and scatter off a lot of things, it can create a kind of glare known as bluehaze. The yellow tint virtually eliminates the blue part of the spectrum and

has the effect of making everything bright and sharp. (Read Why is the sky

blue? for more information on this effect.) That is why snow glasses are

usually yellow. This tint really distorts color perception, which makes it

inappropriate for any activity that relies on accurate color.

Amber and brownish tints are also good general purpose tints. They have

the added benefit of reducing glare and have molecules that absorb higher

frequency colors, such as blue, in addition to UV rays. There has been

research that suggests that near-UV light frequencies such as blue and

violet can contribute to the formation of cataracts over time. In fact, Sun

Tiger has a patent on a particular version called Blue Blockers. These

sunglasses also distort colors similar to yellow lenses, but increase contrast

and clarity.

Green tints on lenses filter some blue light and reduce glare. Because

green tints offer the highest contrast and greatest visual acuity of any tint,

they are very popular.

Purple and rose tints offer the best contrast of objects against a green or

blue background. They make a good choice for hunting or water skiing.

Many manufacturers employ a process called constant density to tint the

lenses. It is the oldest method of creating sunglasses and involves a glass or

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polycarbonate mixture with a uniform colour throughout the material. The tint is

built into the lenses when they are created.

Tinting can also be accomplished by applying a coat of light-absorbing molecules

to the surface of clear polycarbonate. The most common method for tinting

polycarbonate lenses is to immerse the lenses in a special liquid containing the

tinting material. The tint is slowly absorbed into the plastic. To make a darker tint,

the lenses are simply left in the liquid longer.

Polarization Light waves from the sun, or even from an artificial light source such as a light

bulb, vibrate and radiate outward in all directions. Whether the light is

transmitted, reflected, scattered or refracted, when its vibrations are aligned into

one or more planes of direction, the light is said to be polarized. Polarization can

occur either naturally or artificially. You can see an example of natural

polarization every time you look at a lake. The reflected glare off the surface is

the light that does not make it through the "filter" of the water, and is the reason

why you often cannot see anything below the surface, even when the water is

very clear.

A polarized filter passes only the light that does not match its orientation. Only

the part of the light wave that is not aligned with the slots in the filter can pass

through. Everything else is absorbed. The light coming through the filter is

considered polarized. Polarized filters are most commonly made of a chemical

film applied to a transparent plastic or glass surface. The chemical compound

used will typically be composed of molecules that naturally align in parallel

relation to one another. When applied uniformly to the lens, the molecules create

a microscopic filter that absorbs any light matching their alignment. Most of the

glare that causes you to wear sunglasses comes from horizontal surfaces, such

as water or a highway. When light strikes a surface, the reflected waves are

polarized to match the angle of that surface. So, a highly reflective horizontal

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surface, such as a lake, will produce a lot of horizontally polarized light.

Therefore, the polarized lenses in sunglasses are fixed at an angle that only

allows vertically polarized light to enter. You can see this for yourself by putting

on a pair of polarized sunglasses and looking at a horizontal reflective surface,

like the hood of a car. Slowly tilt your head to the right or left. You will notice the

glare off the surface brightens as you adjust the angle of your view.

Many sunglasses advertised as polarizing are in fact not polarized. There is a

simple test you can perform before you buy them to ensure that it is the real

thing. Find a reflective surface, and hold the glasses so that you are viewing the

surface through one of the lenses. Now slowly rotate the glasses to a 90-degree

angle, and see if the reflective glare diminishes or increases. If the sunglasses

are polarized, you will see a significant diminishing of the glare.

The illustration shows an example of artificial polarization

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Photochromic / Transition Sunglasses or prescription eyeglasses that darken when exposed to the sun are

called photochromic, or sometimes photochromatic. Developed in the late 1960s

and popularized by Transitions in the 1990s, photochromic lenses rely on a

specific chemical reaction to UV radiation.

Because photochromic lenses react to UV light and not to visible light, there are

circumstances under which the darkening will not occur. A perfect example of

this is when you are travelling in your car. Because the windshield blocks out

most of the UV light, photochromic lenses will not darken inside the car. For this

reason, most sunglasses with photochromic lenses also have a certain amount of

tint already applied to them.

Photochromic lenses have millions of molecules of substances, such as silver

chloride or silver halide, embedded in them. The molecules are transparent to

visible light in the absence of UV light, which is the normal makeup of artificial

lighting. But when exposed to UV rays in sunlight, the molecules undergo a

chemical process that causes them to change shape. The new molecular

structure absorbs portions of the visible light, causing the lenses to darken. The

number of the molecules that change shape varies with the intensity of the UV

rays.

When you go indoors and out of the UV light, the reverse chemical reaction takes

place. The sudden absence of UV radiation causes the molecules to "snap back"

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to their original shape, resulting in the loss of their light absorbing properties. In

either direction, the entire process occurs very rapidly.

In the PhotoBrown and PhotoGrey products made in the 60’s, the lenses were

made of glass, and the molecules were distributed evenly throughout each entire

lens. The problem with this method became apparent when it was applied to

prescription glasses, in which different parts of the lens can vary in thickness.

The thicker parts would appear darker than the thinner areas. But with the

increasing popularity of plastic lenses, a new method has been developed. By

immersing plastic lenses in a chemical bath, the photochromic molecules are

actually absorbed to a depth of about 150 microns into the plastic. This proved to

be much better than a simple coating, which would only be about 5 microns thick

and would not provide enough molecules to make the lenses sufficiently dark.

This plastic lens absorption process has been popularized by Transitions, the

leading manufacturer of photochromic lenses.

When you choose Transitions Lenses, you choose visual quality, visual comfort

and convenient protection with these performance features:

Virtually as clear as regular clear lenses indoors

Even clearer with an anti-reflective coating

As dark as most sunglasses outside in bright light

Fast to activate

Fast to fade back

Block 100% of harmful UV rays

Reduces the effect of glare

Reduces eye fatigue

Improve contrast

Offer the right tint at the right time in changing light

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Mirror Coating Reflective sunglasses often have a mirrored look. The lenses in these

sunglasses have a reflective coating applied in a very thin, sparse layer -- so thin

that it is called a half-silvered surface.

The name "half-silvered" comes from the fact that the reflective molecules coat

the glass so sparsely that only about half the molecules needed to make the

glass an opaque mirror, are applied. At the molecular level, there are reflective

molecules speckled all over the glass in an even film but only half of the glass is

covered. The half-silvered surface will reflect about half the light that strikes its

surface, while letting the other half go straight through.

Often, the mirror coating is applied as a gradient that gradually changes shades

from top to bottom. This provides additional protection from light coming from

above while allowing more light to come in from below or straight ahead. This

means that if you are driving, the sun's rays are blocked but you can see the

dashboard. Sometimes the coating is bi-gradient, shading from mirrored at top

and bottom to clear in the middle.

The key problem with reflective sunglasses is that the coating is easily scratched.

Apparently, sunglass manufacturers have not been able to successfully apply a

scratch-resistant layer on top of the reflective coating. Therefore, the scratch-

resistant coating is applied first to protect the lenses and the reflective coating is

applied over it.

Scratch-resistant or Hard Coating While glass is naturally scratch resistant, most plastics are not. To compensate,

manufacturers have developed a variety of ways to apply optically clear hard

films to the lens. Films are made of materials such as diamond-like carbon (DLC)

and polycrystalline diamond. Through a process of ionization, a thin but

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extremely durable film is created on the surface of the lens. Hard coatings

increase the resistance of the lens and help to prevent scratching.

Anti-reflective Coating Anti-reflective surface coating is one of the most important components of lens

quality. It is difficult to imagine the lens of a camera, camcorder or binoculars

without this kind of lens treatment. Recently, car windows have also begun

to be coated with anti-reflective coatings. Naturally, spectacle lenses

are not an exception. Anti-reflective coating here is as important for increasing

image quality as in any other optical field. Moreover, in spectacle optics anti-

reflective coating also has medical, cosmetic and esthetic importance.

The purpose of anti-reflective coating is to eliminate reflections on lens surfaces,

thus increasing lens transparency. The principle operation of anti-reflective

coatings is as follows: an extremely thin, invisible layer of metal, sprayed

in vacuum on both surfaces of the lens (the outside and the inside, the latter

being at the side of the eye), reflects light rays as well as the lens surface itself.

At the same time, the thickness of the coating is comparable with a half-length

of the light wave. This is why light waves reflected from both the lens surface

and the surface of the anti-reflex coating superimpose and compensate each

other, and the reflection disappears. The light from different parts of the spectrum

has different wavelengths and that is why any specific coating eliminates only

one specific color component of the reflection completely. The other colors

are still reflected, to some degree, depending on their wavelengths. Thus,

in the end, the reflections in lenses with anti-reflex coating do not completely

disappear, but become noticeably weaker and gain a common coloring that

depends on the thickness of the coating.

The most popular are anti-reflective coatings with a blue-violet residual glare;

green anti-reflexes are also frequent, as well as anti-reflective coatings with soft

golden residual reflections; other shades are also possible.

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There also are more expensive multi-layer anti-reflective coatings. With these

coatings, different layers extinguish different spectrum components of reflections;

the leftover reflections are almost invisible and have a dark gray color. A clear

lens with multi-layer anti-reflective coating can be almost invisible.

Lenses without anti-

reflective coating.

With anti-reflective

coating applied to the

lenses.(Photos

courtesy Essilor.)

The advantages of anti-reflex are:

Lens transparency is increased by 8-10%. The lack

of irritating glares on the inside surface lowers

the load on the brain’s compensatory functions

and decreases fatigue.

Due to increased transparency and lack of visual

interferences, lenses with anti-reflective coating

are much more comfortable for your eyes.

During the dark hours of the day, lenses with anti-

reflective coating improve car drivers’ vision.

The residual colored reflections in lenses with anti-

reflective coating can combine well (or beautifully

contrast) with the color accents of your frame.

And last but not least, by delicately adding more

overtones and depth to the overall esthetic

impression made by the frame, anti-reflective

coatings make spectacles look more modern, “hi-

tech,” and, at the same time, more refined.

Driving without / with AR Coated lenses

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VP Coating (ViewProtect) One of the biggest complaints from wearers of AR coatings is that they feel they

have to clean their lenses constantly because they can see dust and dirt on the

surface. ViewProtect is a top layer that optimises visual performance and

comfort, whilst reducing lens maintenance time. ViewProtect is a super smooth

coating with a number of advantages.

The primary advantages of Hi Vision ViewProtect:

Easy to clean - reducing lens maintenance time

Water and grease-repellent - condensation is reduced when moving

between temperatures

Attracts less dust and dirt - the lens stays cleaner for longer

You'll look great! - see your eyes, not the reflection

Your lenses will last longer - with this hardwearing, tough, durable,

scratch resistant coating

You'll have comfortable vision - glare and surface reflections are

minimised, especially when driving at night

Ultraviolet Coating Several of the most serious eye problems can be linked to one cause: UV light.

UV is often separated into two categories based on the frequency and

wavelength of the light: UV-A and UV-B.

As a natural protection mechanism, the cornea of your eye absorbs all of the UV-

B and most of the UV-A light. But over time, this absorption can lead to cataracts.

And the small amount of UV-A which gets past your cornea, can eventually lead

to macular degeneration, the leading cause of blindness in people older than age

65. Intense and prolonged exposure to UV radiation can cause either cancer of

the eye or photokeratitis, which is basically sunburn on your retina. Because it

occurs most often when a person is outside on a bright winter’s day with sunlight

glaring off the snow, this condition is commonly known as snow blindness.

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Correcting lenses and sunglass lenses protect the eyes from UV rays, but they

do not always have the same efficiency. The degree of UV protection provided

by eyewear is usually measured in percent (100% — full protection). Quite often

the protection against two ranges of UV radiation — soft and hard — is indicated

for lenses. Not all lenses provide sufficient UV protection — it is possible that

cheap sunglasses from a street market do not protect the eyes at all, even if they

have a “UV — 100%” sticker on them. Corrective lenses do not necessarily

protect the eyes from UV rays. The degree of the lenses’ UV protection depends

on the material from which the lenses are made, lens coloring and whether

the lenses have anti-reflex coloring of a certain type. However, with

any combination of these parameters the lenses can be covered with a special

coating that guarantees almost 100% UV protection. High-quality lenses

are usually supplied with this coating; if it is absent, you can order

it as an additional option.

Water repellant coating The very slippery coating is easier to clean but has no real advantage in water

repellence. These lens surface coatings are advertised by some manufacturers

as a means of preventing lenses from steaming up. However, experience shows

that such coatings do not work for long. You will also find it difficult to apply

markings on the lens.

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2. UNDERSTANDING PRESCRIPTIONS

LENS POWERAs light rays passes through a lens with power, the rays are bent or refracted. In

a lens with a plus power, the light rays converge or are refracted towards one

another. The point at which the light rays converge is called the focal point and in

a plus lens, is behind the lens surface. In a lens with a minus power, the light

rays diverge or are refracted away from one another. If these rays are

extrapolated or traced back towards the light source, the lines will converge and

form a focal point in front of the lens surface.

The lens power is relative to the focal distance or the distance between the focal

point and the lens. More specifically, lens power is the reciprocal of the focal

distance in meters. Lens power is expressed in diopters (D).

The Prism DiopterOne prism diopter is defined as the prism power needed to deviate a ray of light 1

centimeter at a distance of one meter.

26

The best way to understand the behavior of light through a curved lens is to

relate it to a prism. A prism is thicker at one end, and light passing through it is

bent (refracted) towards the thickest portion. See the diagram below.

A lens can be compared to two rounded prisms joined together. Light passing

through the lens is always bent toward the thickest part of the prisms.

To make a minus lens (diagram - left), the thickest part, the base, of the prisms is

on the outer edges and the thinnest part, the apex, is in the middle. This spreads

the light away from the center of the lens and moves the focal point forward. The

stronger the lens, the farther the focal point is from the lens.

To make a plus lens (diagram - right), the thickest part of the lens is in the middle

and the thinnest part on the outer edges. The light is bent toward the center and

the focal point moves back. The stronger the lens, the closer the focal point is to

the lens.

Placing the correct type and power of lens in front of the eye will adjust the focal

point to compensate for the eye's inability to focus the image on the retina.

27

Determining Lens Strength The strength of a lens is determined by the lens material and the angle of the

curve that is ground into the lens. Lens strength is expressed as diopters (D),

which indicates the extent in which light is bent. The higher the diopter, the

stronger the lens. Also, a plus (+) or minus (-) sign before the diopter strength

indicates the type of lens.

Lens Shapes Two basic lens shapes are used in optometry: spherical and cylindrical.

SPHERICAL LENS This lens looks like a basketball cut in half. The curve is the same all over the

surface of the lens. Spherical lenses act equally in all directions; they magnify, or

correct blur the same amount in every direction.

An ordinary magnifying glass is a kind of spherical lens. When a spherical lens

acts as a magnifier, it magnifies equally in all directions. In the diagram below,

the magnified letters are magnified both in height and in width.

When a spherical lens puts an optical system out of

focus and introduces blur, it blurs equally in all

directions.

This is how this kind of blur looks on an eye chart.

This blur involves no astigmatism at all. Note that

it is equally blurred in all directions.

28

CYLINDRICAL LENS A cylindrical lens looks like a pipe cut lengthwise. The direction of a cylinder

curve's spine (axis) defines its orientation. It will only bend light along that axis.

Cylinder curves are commonly used to correct astigmatism, as the axis can be

made to match the axis of the aberration on the cornea.

Some kinds of magnifying glasses, made specifically for reading wide columns of

print, are cylindrical lenses. When a cylindrical lens acts as a magnifier, it

magnifies only in one direction. In the diagram below, the magnified letters are

only magnified in height, not in width.

When a cylindrical lens puts an optical system out of focus and introduces blur, it

blurs only in one direction:

This is the kind of blur you get from astigmatism. The

letters are smeared out directionally, as if an artist had

rubbed his or her thumb across a charcoal drawing. A

cylindrical lens of the right strength can correct this kind

of blur.

This is how this kind of blur might look on an eye chart:

Compare it to the kind of blur that is equally blurred in

all directions.

When an optometrist refracts your eyes, usually he or she begins by finding the

best spherical correction. If there is astigmatism, the next step is to remove it by

adding the right amount of cylindrical correction.

29

HOW TO READ THE PRESCRIPTION

Most prescriptions have four parts:

The base (spherical) strength and type (plus or minus)

The cylinder strength and type

The cylinder axis orientation (in degrees with 90 degree being vertical; an

"x" means "at")

The strength of bifocal segment ("plus" indicating "in addition") and type

And in case you have ever wondered, OD means right eye and OS left eye.

A short form prescription from the optometrist might read:

+2.50 -0.50 x 10 add +2.50

This means:

A +2.50D spherical base curve (plus lens)

A -0.50D cylinder at 10 degrees (a minus cylinder lens is added to the base

curve)

An additional bifocal segment of +2.50D

When working with the script of a patient and having to order different types of

lenses, the following rules apply:

Distance glasses: Use script as is – ignoring the add.

Reading glasses: Deduct the smaller spherical power from the larger one and

use the larger figure’s symbol (+ or -). If the symbols are both plus (+), add it

together.

I.e.: -2.75 -0.50 x 175 add +2.50 – The reading scrip will be:

-2.75 -0.50 x 175

+2.50

-0.25 -0.50 x 175

30

Or: +1.00 -0.50 x 175 add +2.50

Or: -1.00 -0.50 x 175 add +2.50

Bifocal & Multifocal: Use the prescription as is. The lens lab will do the

necessary calculations.

More examples:

Example 1: Sphere Cyl Axis Add

R +2.50 -0.50 10 +2.50 L +2.75 -0.50 175 +2.50 PD: 66/63

Distance script: R +2.50 / -0.50 x 10 PD 66 L +2.75 / -0.50 x 175

Reading Script: R +5.00 / - 0.50 x 10 PD 63 L +5.25 / - 0.50 x 175

Example 2: Sphere Cyl Axis Add

R -2.50 -0.50 10 +2.50 L -2.75 -0.50 175 +2.50 PD: 66/63

Distance script: R -2.50 / -0.50 x 10 PD 66 L -2.75 / -0.50 x 175

Reading Script: R 0.00 / - 0.50 x 10 PD 63 L -0.25 / - 0.50 x 175

+1.00 -0.50 x 175

+2.50

+3.50 -0.50 x 175

-1.00 -0.50 x175

+2.50

+1.50 -0.50 x 175

31

Now you do it:

Example 1: Sphere Cyl Axis Add

R -1.75 -0.50 10 +2.50 L -1.50 -0.50 175 +2.50 PD: 65/62

Distance script: R _________________________ PD ____

L _________________________

Reading Script: R _________________________ PD ____

L _________________________

Example 2: Sphere Cyl Axis Add

R -6.75 -0.50 10 +2.50 L -5.50 -0.50 175 +2.50 PD: 64/61

Distance script: R _________________________ PD ____

L _________________________

Bifocal Script: R _________________________ PD ___/___

L _________________________

Example 3: Sphere Cyl Axis Add

R +2.25 -0.50 10 +2.75 L +2.25 -0.50 175 +2.75 PD: 65/62

Distance script: R _________________________ PD ____

L _________________________

Reading Script: R _________________________ PD ____

L _________________________

32

Example 3: Sphere Cyl Axis Add

R -3.50 -0.50 10 +2.50 L +2.75 -0.50 175 +2.50 PD: 65/62

Distance script: R _________________________ PD ____

L _________________________

Reading Script: R _________________________ PD ____

L _________________________

33

WRAP PRESCRIPTIONS It's easy to understand the popularity of wrap sunglasses. The curved, contoured

eight-base polycarbonate lenses in most wraps block UV, shield the wind, reduce

glare and protect from impact. They provide excellent optics tailored to all sorts of

outdoor conditions, whether cycling, golfing, hiking or fishing. They are designed

to be light weight, comfortable and versatile.

Wrap effects and optimization The curvature and wrap that makes the lens so functional in terms of lens

coverage also requires care in setting up the Rx. Compared to a standard "flat"

lens in the same Rx, a wrap lens changes the base curve and tilts the lens in the

vertical plane. These changes will affect the wearer's vision, not usually for the

better, unless the optics are optimized for the effects of wrap. Fortunately, the

optimization is well understood.

Tilt (wrap) optimization The primary optical effect of wrapping a powered Rx lens is an offset in the prism

and power of the lens as perceived by the wearer. The fact that the wearer looks

through a lens differently when it is wrapped is key. To consider it another way, if

you take an ordinary "flat" lens of a certain Rx power and introduce wrap tilt, the

lens will still read the original Rx only when measured along the original OC and

visual axis of the lens. However, in the new wrap configuration the wearer is now

looking through the lens on a different optical axis corresponding to the wrapped

positioning.

The resulting prism and blur can be objectionable, especially in higher powers.

Even a plano lens introduces prism when wrapped, causing discomfort for the

wearer; this is why so many ophthalmic manufacturers of better sunglasses

provide decentered (i.e. prism corrected) lenses in their plano sports eyewear. In

an Rx lens, the lens power makes those effects even stronger.

34

Fortunately, the corrections required to optimize the wrap are fairly

straightforward and formulas can be found in many ophthalmic optical texts. The

calculation takes into account the Rx power and the wrap dimensions of the

frame and the resulting optimization usually adds some base-in prism at the eye

point and small adjustments of power, cylinder and axis compared to the original

"flat" Rx. These adjustments are ground into the Rx during surfacing.

There are two interrelated issues dispensers must be aware of when ordering

wraparound lenses. The first concerns the front base curve of the lens, which

must conform to the wraparound frame design instead of the patient’s

prescription. This means that prescriptions, such as -2.50D, normally on a four

base curve, must be ground on an eight base lens for wraparounds. These

steeper base curves are not the optimum for the patient’s Rx and can cause

peripheral distortions.

The second ordering issue concerns the wrap angle of the frame, generally 13 to

23 degrees. This angle rotates the optical axis of the lens toward the temporal

area and creates power errors and unwanted prism.

The goal of wraparound lens processing is to compensate for the optical

problems caused by the steeper base curve and wrap angle. In order to minimize

unwanted prism and power error in the patient’s straight-ahead vision and reduce

peripheral distortions, optical labs must take into account:

prescription power,

the patient’s monocular PD and the

measurements of the frame

when selecting and processing the wraparound sunlens.

The optical effects of steeper base curves and wrap lenses can be minimized if

the dispenser conveys exact prescription and frame information to the optical lab,

and then has an in-depth discussion with the optical lab about lens options for

35

the individual patients. Dispensers have the responsibility to advise patients that

their eyes may not accommodate to this minimal peripheral blur immediately.

Tell the patient that it may take a couple of days to get used to the wraparound

lens and that it may seem different at first.

There are always high-maintenance patients and sometimes a dispenser needs

to steer them away from this product. However, if you advise the patient,

especially those in a higher power, that it can take them a couple of days to get

used to the lenses, the vast majority of the patients are fine.

Changing Curves Hyperopes have fewer issues than myopes because plus powers typically use

front base curves of six and higher, so the base curve switch is not as severe.

Most dispensers are hesitant to fit moderate-to-high hyperopes with wrap

sunlenses—edges can be too thin to mount—but Rxs of +2.00D and below have

few problems. The point to remember is to order a spherical, not aspherical

product.

For myopes the base curve change is dramatic. In general, base curve is

determined by a prescription. In the case of wraps, however, base curve is

determined by the cosmetics of the frame.

Lens manufacturers offer front base curves in one to two diopter steps. The

higher the value, the steeper the curve. Manufacturers differ in how they specify

their base curves. Dispensers should review the seven to nine base availability of

the lenses they prefer for the patient.

Most wrap sunglasses requires an eight base curve. But there are six base curve

wraps and even some 10 base frames. These are typically plano although more

ambitious dispensers and labs have had success with mounting prescriptions in

these “severe wrap” frames. Use a lens clock to measure the front base curve of

36

the frame’s demo lens and, with your lab, find a

lens that will best match that curve and still be

able to contain the patient’s prescription.

Due to the need for steeper curves, there are

general prescription limitations for wrap

sunglasses: +2.00D to a -4.00D sphere and

cylinder powers up to -2.00D. These are more

rules of thumb than written in stone. Other factors,

such as eye size, frame design and patient PD

play significant roles in determining if a wrap lens can be processed. It requires

discussing the prescription—and frame selection—with the lab.

In lens processing, the lab grinds a back curve on the lens and the prescription is

essentially a combination of the front and back curves. Some eight base blanks

will not be thick enough for higher minus prescriptions or the lens edges will be

too thick for mounting.

Sometimes it’s necessary to choose a different type of lens. For example,

polarized lenses, which are typically in an eight base curve for wraps, may not be

the best lens choice for patients with prescriptions above a -3.00D with a cylinder

power of -2.00D. For these patients we suggest going to polycarbonate or high-

index material, generally 1.60. “There are some high-index manufacturers that

produce a 7.25 base curve, which will fit nicely in most wraps and still

accommodate the Rx,” he explains. “The thinner material will mean less steep

curves, edges are thinner and the lens won’t pop out of the frame.”

Ordering Prism Choosing a base curve to match the frame curve is only part one of the ordering

process. In wrap styles, the optical axis of the lens rotates more temporally than

in other frame styles because of the frame’s wrap angle. This causes unwanted

Lens Clock

37

prism and shifts decentration. In a wrap design, the eye is looking through the

lens differently than in other lenses and prescriptions have to be adapted to

these changes. For most myopic prescriptions, a compensating prism—base in

prism—must be ground into the lens to enable the patient to see through his or

her wraparound sunwear just like they do through flatter more typical styles.

Base in prism, which is ordered in 1/4 diopter steps, reduces the prismatic effect

that comes from rotating lenses in wrap sunglasses. The rule of thumb is, for

powers less than 2.50 diopters, use a 0.25 prism diopters base in. For

powers 2.50 and greater, order 0.50 prism diopters base in.

Consider Measurements Even powers on the high end or just outside recommended prescription range

can be used for wraparounds, as long as such things as patient PD, frame

measurements and the direction of lens power is taken into consideration. If the

cylinder power is too high in the 90 degree meridian, then we may start looking at

using a lower curve than an eight base. We have to discuss the frame with the

dispenser to see if it can handle a less steep lens and still have the same

cosmetics.

In addition to the prescription power, the patient’s PD is a factor in determining

wraparound sunglasses. In general, a 58 PD or narrower can pose problems, but

those problems can be mitigated by prescription power and/or wraparound frame

dimensions. A wider PD won’t be as much of a problem with a lower prescription.

Dispensers should suggest a smaller eye size, which can also compensate for

the narrow PD as well as the Rx. Too narrow a PD and a large frame may cause

problems such as too thick edges, not enough lens diameter or not enough blank

thickness. Too large a PD and a large frame could mean not enough blank

diameter or thickness, and the inside bevel of the frame may be unable to secure

the lens. Certain edge thicknesses in minus Rx’s may not allow the temples to

close.

38

Technical Tips for Wrap Sunglasses

Take monocular PD’s.

Inform patients there will be an adaptation process.

Sell Rx wrap sunglasses only when there is already a working prescription.

It is not recommended to have patients adapt to both wrap sunglasses

and a new Rx at the same time.

Avoid dispensing lenses outside of the range +2.00D to -4.00D sphere,

with cylinders to -2.00D.

Wraps with smaller eye sizes or a less severe tilt work best for stronger

powers or narrow PD’s.

39

3. PD MEASUREMENTS & SEG HEIGHTS

The Optical Centre of a lens is the point of optimum vision since it is the single

point through which light may pass without being deviated. After passing through

the spectacle lens, light enters the eye through the pupil. Pupillary

measurements are important because they allow the laboratory to situate the

optical centers of the finished lenses directly in front of the pupils. An accurate

pupillary measurement is one of the first steps to achieving good visual clarity.

There are two types of pupillary measurements – binocular and monocular. A

binocular measurement is the single overall distance from pupil to pupil. The

monocular measurement is the combined individual distance from the centre of

the bridge to the centre of each pupil.

Important notice: Never take papillary measurements before the frame has been

fully adjusted to fit the patient’s face!!

Binocular PD (65)

Monocular PD (34/31)

40

Binocular Pupillary Measurements

Equipment : PD Ruler

Positioning : Eye to eye with patient at approximately 40 cm

Technique : 1) Place PD ruler on patient’s bridge

2) Close your r-eye and instruct the Px to look at your open

l-eye

3) Center the zero mark in the centre of the right pupil

4) Close your left eye, open your right eye, and instruct the

patient to look into your open right eye

5) Note the millimeter indicator that directly centers over the

left pupil. That number is the binocular pupillary

measurement.

Alternative : 1) Some dispensers find it easier to, instead of pupil to

pupil, measure from the outside of one iris to the inside

of the other iris – on the limbus. This method is

recommended when dealing with patients with a very

dark eye colouring.

41

BINOCULAR PUPILLARY DISTANCE MEASUREMENT

Equipment: PD Ruler

Positioning: Eye to eye with patient at a distance of approximately 40cm

Technique: Place pd ruler on px’s bridge. Close your right eye and instruct

patient to look into your open left eye. Place the zero mark on the outside of the

iris of the patients’ right eye (left in front of you)

Then - close your left eye and ask the patient to look into your open right eye. Do

not move the PD Ruler. Note the millimetre indicator directly on the incide of

the iris of the patients’ left eye (on your right). That number is the binocular

pupillary measurement.

0lllllllll1lllllllll2lllllllll3lllllllll4lllllllll5lllllllll6lllllllll7lllllllll8lllllllll9lllllllll10lllllllll11lllllllll12lllllllll13llllllll14lllllllll15

0lllllllll1lllllllll2lllllllll3lllllllll4lllllllll5lllllllll6lllllllll7lllllllll8lllllllll9lllllllll10lllllllll11lllllllll12lllllllll13llllllll14lllllllll15

42

MONOCULAR PUPILLARY MEASUREMENTS

Equipment: Corneal Reflection Pupillometer. This device will automatically take

both monocular and binocular measurements. The accuracy of this device is

unparalleled and should be the primary source of pupillary measurements for

multifocal wearers.

Adjust the frame

Adjust the frame on the patient for maximum comfort

and accuracy before taking any measurements.

Set the vertex distance between 12 and 14 mm.

Set the pantoscopic tilt angle between 10 and 12

degrees.

Frame should have positive facial wrap.

Take Patient's Pupilary Distance (P.D.)

Always take monocular PD to ensure exact centering of

the eye behind the lens.

Multifocal lenses should be fitted using distance

monocular PD.

Or – use a manual procedure: Take the Fitting Height Measurement

Allow for frame slippage and avoid parallax error.

Take a monocular height measurement by marking each

lens at center pupil using a felt tip pen.

Draw a horizontal line on each lens and double-check to

make sure that the lines are crossing the center of each

pupil.

Measure the fitting height from the deepest point of the

lens to the pupil center.

43

Determine lens blank size

Mark the patient's fitting height and distance P.D. on the

sample lens, creating a cross.

Place the lens cross over layout-chart cross to verify

that the lens will fit into the frame.

If the lens does not fit, choose another, more suitable

frame that will accommodate the lens.

Manual Procedure:

Equipment: Permanent marking pen and adjusted frame on patient’s face

Positioning: Eye to eye with patient on an equal level - NO parallax. The

success of the measurement depends on this fact.

Technique:

1. Position your hand holding the permanent marker pen over the patient’s

right eye – ready to mark the right dummy lens.

2. Ask the patient to look into your open left eye.

3. Find the patient’s pupil and make a dot on the dummy lens exactly in front

of the middle of the pupil.

4. Now ask the patient to look into your open right eye and repeat the

procedure.

5. Remove the frame from the patient’s face and, on the back of the right

dummy lens using your Pd ruler and marker pen; draw a horizontal line

(about 0.5 cm) through the dot.

6. On the front of the dummy lens, draw a vertical line on the dummy lens

through the dot. Your lens now has a clear cross on it.

7. Repeat the process on the left dummy lens.

8. Place the frame back on the patient’s face.

9. Resume your initial position in front of the patient and ask him/her to look

into your open left eye.

44

10. The cross must now be exactly in the middle of the pupil.

11. Repeat the process on the left lens.

12. Should any of the markings not be directly in front of the pupil, determine

whether it is the horizontal line or the vertical line that is out of place.

Remove only the incorrect line and repeat the process above.

13. Do not stop the process until the crosses are perfectly positioned in front

of the pupils.

14. Leave the markings on the dummy lenses for the lab technician.

15. Record the measurements on the patient card as follows (not the callouts):

45

SEGMENT HEIGHTS

The patients ability to wear and work comfortably with a set of multifocal lenses,

often hinges upon the accuracy with which the segments are fitted. One of the

most common causes of multifocal discomfort is inaccurate segment placement.

There are many rules of thumb that attempt to pinpoint the proper location of any

given segment. Many of these rules are merely generalities that were formulated

in a market atmosphere very different from that of today. For example, one of

the most famous rules read: “Segment height should be 3mm bellow”. This rule

implies that, if the top of the segment is placed 3mm below the horizontal

midpoint of the lens, the wearer will experience comfortable near vision. In the

days of 46- and 48mm eye frames this rule probably worked more often than not,

but with today’s smaller frames, this rule lacks credibility. The only rule to

remember when fitting multifocals is: “Everyone is different and the best segment

height is the one that works best for the patient”.

Segment height should be determined by working with the patient, their properly

adjusted frame of choice, and a P.D. Rule. The industry recognises segment

heights as the millimeter distance from the lowest point of the eye wire to the top

of the segment. This distance is not necessarily from the bottom of the segment

to the top of the segment.

Segment Height Measuring:

Equipment : P.D. Rule and properly adjusted frame of choice

Positioning : Eye to eye with patient at a distance of approximately 40mm

Technique : 1) With frame properly adjusted, place the zero reading of

the P.D. Rule at the desired location of the segment top.

2) Look down to lowest point of eye wire. Reading on P.D.

Rule at that point is the seg height.

Note : If at the time of measurement the frame is not resting where

it will normally be worn, the reading will be inaccurate.

46

Alternatives : If seg height measurements are needed on a frame without

lenses, place a piece of clear tape vertically across properly adjusted frame.

With frame on, use a permanent marker pen to mark desired height. Remove

frame to measure from lowest point on eye wire to reference mark. This

technique is particularly helpful for locating papillary heights when filling

progressives since it automatically isolated both horizontal and vertical co-

ordinates.

Diagram to demonstrate measurements:

Recording measurements:

R L

18

3134

17.5

Desired Seg Height MULTIFOCAL

Frame rim

Desired Seg Height BIFOCAL

Desired Seg Height TRIFOCAL

Seg Height - L

Monocular PD - L

Seg Height - R

Monocular PD - R

47

MULTIFOCAL FITTING ON COLLECTION:

Confirm Fit On The Patient

With lenses marked or using decals, verify that the

fitting cross is at pupil center.

Adjust the frame to raise or lower the fit, if

necessary.

Demonstrate Viewing Area

Demonstrate the nearprescription by letting the

patient read a reading

card.

Repeat the

demonstration. This time

ask the patient to look at

an object at arm's lengthdistance.

Demonstrate the new,

clear distance prescription

by having the patient look

at an object at least 6 meters away.

Periphery Demonstrate the decrease in power at the periphery by having the patient hold his head

still while moving the reading card from side to side. Ask the patient to point his nose

towards the direction of the print especially at the periphery. Finally, provide the patient

with a brochure on how to use his/her new Multifocal.

48

FITTING PROBLEMS

SYMPTOM SOLUTION

Patient has narrow

reading area.

Add Pantoscopic tilt and decrease vertex distance.

Check fitting height. Show patient where to view

near, intermediate and distance. Demonstrate the

use of his/her new lens. Double check add power.

Peripheral vision blurs

and moves.

Adjust frame to decrease vertex distance and to

increase frame wrap.

Patient lifts head or

glasses to read.

The lenses are fit too low. Adjust frames or refit

lenses. Adjust nose pads.

Patient lowers head or

glasses to see at

distance.

The lenses or glasses are too high. Adjust frames

or refit lenses. Adjust nose pads.

Patient moves reading

material off to side for

better focus.

PD. is off (check each eye separately.) Submit

correct PD measurement and have lenses

remade.

Distance vision is slightly

blurry.

If reference is to side vision, increase face wrap. If

primary gaze is blurred, increase pantoscopic tilt

or widen bridge to decrease lens fitting height

slightly. Reassurance and frame adjustment will

usually solve this issue. Ensure .25 diopter not

added to Rx.

49

4. USING A LENSOMETER / VERTOMETER

The Lensometer is an instrument with which we can inspect lenses for:

Total dioptric power

Add power

Axis and alignment

Optical centre placement

Prismatic effect

As a measure of total dioptric power, this instrument measures focal length which

is the result of a combined front and back curve. Through an optical system with

a moving lighted target, the Lensometer reads the focal length of a lens and then

translates the reading into dioptric values which are registered on a dial of the

power drum.

The target has a dual element, one for sphere powers and one for cylinder

powers. This target is superimposed on a series of concentric circles called the

reticle, each of which represents a dioptric value.

Sphere target

Reticle

Sphere target

4 3 2 1 ½

50

Procedure Adjust the eyepiece of the empty lensometer until “Plano” is in focus.

Place the back side of the lens against the lens stop and situate the lens

so that the target is centered over the reticle.

Turn the axis wheel and power drum until the target is in focus.

When you look into the lensometer eyepiece, you will notice a target or reticule

similar to the one pictured below. It will have degree marks and a diopter scale

that can be rotated using a wheel on the eyepiece head.

Focus the single line mire and the double line mire. Notice where the two mires

intersect. If the lens is spherical, the mires will form a focused intersection.

If the lens is cylindrical, the single line mire and the double line mire will not be in

focus at the same time. The first reading from a compound lens should be the

singular line or the spherical element of the target. This reading will convey the

dioptric power of the sphere and may be read directly from the power drum. The

amount of cylindrical power will be determined by re-turning the power drum until

51

the multiple lines or the cylinder element of the target is in focus. The amount of

the cylinder power is the difference between the first and second reading. The

number of increments moved on the dial will equal the number of diopters of

cylindrical power. In addition to the amount of cylinder, the plus or minus value

of that cylinder is determined by the direction the drum is turned to focus the

second target.

Movement on Power Drum Cylinder Sign From Plus to greater Plus +

From Plus to lesser Plus -

From Minus to greater Minus -

From Minus to lesser Minus +

Measuring Bifocal addition Bifocal additions may also be read with a lensometer; however, the procedure for

doing so is slightly different because the distance power is a measure of focal

length or back vertex while bifocal additions are a measure of the front vertex.

Distance power indicates how far behind a lens parallel beams of light will focus

to a point. Add power is calculated on how far in front of a lens a near object

must be held so that light rays diverging from it may be brought to focus.

Parallel beams from distance

Front Vertex

Back Vertex

Diverging beams from near

X

52

To accurately read the add power off a lens:

Place the front side of the lens against the lens stop. Centre the distance

optical centre over the lens stop. Take a spherical reading

Carefully raise the lens in order to take a sphere reading through the add

Subtract the smaller number from the larger number. The answer will

always have a plus sign designation and be equal to the true power.

Determining cylinder lens alignment In addition to reading power, the lensometer can also be used to determine

cylinder lens alignment. Cyl power can be located in any meridian from zero to

180º. The axis wheel rotates the target in a circular motion from zero to 180º.

Theoretically the single degree at which the cyl target is unbroken, is the degree

at which the cyl has been ground. This degree which will read out on the axis

wheel should coincide with the axis prescribed by the Optometrist. In reality low

cylinder powers are more difficult to pinpoint since more movement of the wheel

will be needed to break the target lines. Stronger cylinders are easy to pinpoint

since slight rotations of the axis wheel create noticeable breaks in the target

lines.

Example: +2.00 -2.00 x 90

Axis 87º – target broken Axis 90º - in Focus Axis 93º – Target Broken

53

DETRMINING HORIZONTAL PRISM CORRECTION

If there is no prismatic effect in the lens, this intersection will be in the centre of

the target of the lensometer. If there is a prismatic effect in the lens, this

intersection will not be centred in the target of the lensometer.

The image below shows a spherical lens with no prism correction. The centre of

the intersection of the single and triple line mires is centred in the bulls-eye of the

eyepiece target.

The image below shows a cylindrical lens with a prism correction. The single and

triple line mires do not focus at the same time and they have been focused at a

point in-between. A blurry image of the intersection is displaced to the left of the

bulls-eye of the target, indicating that a prism correction is present. The mires are

seen at an angle because of the oblique axis of the cylinder.

54

The distance of the intersection from the centre of the target is a measure of the

strength of the prism. The farther the intersection is away from the centre, the

greater the prism power is.

The diopter scale can be rotated to facilitate measuring the diopter value.

In the example below, you can see that the intersection of the mires lines up with

the target circle marked "2", indicating that there is a two diopter prismatic power.

The direction of the displacement of the intersection from the centre of the target

is an indication of the orientation of the base of the prism. In the example above,

the prism base direction would be "base out", if we are measuring the right lens.

If we are measuring the left lens, the prism would be "base in".

Base-in displacement

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Below: base-out displacement

What is the correct prism reading on the right lens pictured below?

We first notice that there is a prism correction because the intersection of the

mires is displaced to the right from the bulls-eye of the target. Since we are

measuring a right lens, the displacement is nasal, meaning the prism is base-in.

The diopter value is 1.5 because the intersection aligns with the line that is

between the 1 diopter circle and the 2 diopter circle.

We know that there is only horizontal prism correction present because the

displacement is along the 180 degree line.

56

What if there is so much prism correction that the intersection is off the scale?

This situation does arise. The prism may be so strong that the intersection

cannot be located, no matter how the lens is placed. The image in the eyepiece

may look something like this, with perhaps only the triple line mire in view.

When dealing with high diopter prism corrections, a loose prism may be needed

to bring the intersection back onto the scale. Start with a 5 D loose prism and

place it in front of the spectacle lens, over the mark, with the base of the loose

prism opposite from the base direction of the prism being measured.

In this case we are measuring a left lens. The single line target and the

intersection are off the scale to the right, indicating a large base-out prism

correction.

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Place a 5 D prism with the base inward over the mark on the spectacle lens.

Some lensometers have a holder for placing a prism from a trial lens set.

This will bring the intersection back onto the scale, as pictured below.

The auxiliary prism power must be added to the scale reading. In the example,

the intersection is on the 3 D line, so we add 5 D to 3 D to get a total prism

correction of 8 D.

DETRMINING VERTICAL PRISM CORRECTION When measuring vertical prism in a pair of glasses, knowing the patient’s viewing

position through the lenses is not as critical as it is when measuring horizontal

prism. In fact, the total prism correction (right lens prism diopters + left lens prism

diopters) can be found without marking the pupil centre positions on the lenses.

This comes in handy if you are in a hurry and simply want to confirm the total

prism correction. You will, however, need to make the marks in order to find the

precise prism correction in each lens.

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Recognizing the presence of prism in a pair of glasses Each time you read a pair of glasses on a lensometer you should be checking for

the presence of a prism correction. Don’t ever assume that there is no prism

correction in the glasses of a new patient. Many times patients will not volunteer

this information and it may not be obvious from the history or from previous

exams.

The presence of horizontal prism can be recognized because the lens has to be

shifted away from the normal patient viewing area in order to centre the

intersection of the mires in the lensometer target.

For example: Normally, a lens placed on the lensometer stage in such a way that

you can take a reading just above the centre of a flat-top bifocal line, will result in

mires centred in the lensometer target, as pictured below.

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If, however, you find that the intersection of the mires has shifted significantly

away from the target when reading the lens in what should be the proper

position, then you know that there is a prism correction present, as pictured

below.

The key to recognizing the presence of vertical prism in a pair of glasses is to

leave the lens stage in the same position when checking each lens. The lens

stage adjusts up and down.

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For example: The intersection of the mires is centered in the lensometer target

and the right lens prescription is measured.

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Now align the left lens on the lens stage of the lensometer, but do not move the

lens stage up or down from the original position.

Notice whether the intersection of the mires is centred in the lensometer target;

or is the intersection above or below the lensometer target? If it is above or below

the lensometer target, as pictured above, then you know that a vertical prismatic

power is present.

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Measuring the vertical prism correction At this point the total vertical prism correction can be determined simply by noting

the direction of the shift in the left lens and by noting the power as measured by

the diopter markings on the lensometer target. Remember that the intersection of

the mires was centred in the target when we measured the right lens.

The example above shows a vertical shift of the mires. The intersection of the

mires is lined up with the mark that is between the "1" and the "2" measuring

circles on the target. This indicates a prism power of 1.5 D, base-up.

If you want to know the individual prism correction for each eye, you will need to

mark each lens at the point through which the patient views.

Once you have the lenses marked, measure each lens with the mark in line with

the lens port of the lensometer. If base-up prism is present, the intersection of the

mires will be above the target of the lensometer. Rotate the scale (using the knob

on the eyepiece) to a vertical orientation and measure the diopter power from the

scale.

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Now measure the left lens. Line up the mark on the left lens without moving the

lens stage up or down. If the mark is above or below the port, then you know that

either you marked the lens incorrectly, or the patient’s glasses are not properly

fitted to her face. Remark the glasses or adjust the fit as necessary.

Assuming the lens is marked correctly, measure the prism correction in the left

lens. If the prism correction in the right lens is base-up, then either there will be

no vertical prism correction in the left lens (the mires will centre in the target), or

there will be base-down prism in the left lens. The reverse is also true. Base-

down prism in the right lens will mean that there is either no vertical prism in the

left lens, or there is base-up prism in the left lens.

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Add the right and left vertical prism corrections if you want the total vertical

correction. For example: 2 D base-down OD and 1 D base-up prism OS is equal

to 3 D total vertical prism correction. The orientation for the total correction can

either be base-down OD or base-up OS.

Glasses are not intentionally made with base-up prism in both eyes or base-

down prism correction in both eyes. If the glasses measure this way, it usually

means that the patient is viewing (or you are measuring) either above or below

the intended vertical optical centre of the lenses. When measuring a pair of

glasses in this situation, you will need to adjust the lens stage so that either the

mires of the left lens, or the mires of the right lens, line up vertically with the

lensometer target.

Vertical prism correction that is off the scale Occasionally you may encounter vertical prism correction that is off the diopter

scale of the lensometer.

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Just as you did when measuring horizontal prism, you will need to use an

auxiliary prism to bring the image back onto the scale. If the prism direction being

measured is base-down, the auxiliary prism will need to be aligned base-up in

front of the lens port. A 4 D loose prism usually does the trick.

The loose prism will bring the image back onto the scale. Remember that you will

need to add the power of the loose prism to your new scale reading.

In the example above, the 4 D value of the loose prism is added to the scale

reading of 3 prism diopters to give a prism reading of 7 D base-down.

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Test Yourself Mr. Jones wears flat-top bifocals. When checking his vision, you notice that his

line of site is just above the add line, in the middle of the seg. When reading the

right lens on the lensometer you line up the lensometer port just above the seg

line, in the midline of the seg. Below is pictured the image you see when reading

the lens power.

Now you shift the glasses over to read the left lens, without moving the lens

stage up or down. The left lens is aligned in such a way that the lensometer port

is just above the middle of the seg line. The image below is what you see when

looking into the lensometer.

Is there a prism correction in the right lens? How about the left? If there is a

prism correction, what is the direction and power in each lens?

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Answer: There is a prism correction in each lens. The right lens has 2 diopters

base-up prism. The left lens has 1 diopter of base-down prism. The total vertical

prism correction is 3 diopters.

MEASURING A MIXED PRISM CORRECTION

A mixed prism correction is simply a combination of vertical and horizontal prism

correction in the same lens.

Recognizing the presence of mixed prism correction in a pair of glassesAs discussed in the previous Sections, the presence of a prism correction can be

easily recognized when performing manual lensometry. If the lensometer port is

lined up with the point in the lens through which the patient views, then the

intersection of the mires must center with (or be close to) the target of the

lensometer. This condition will indicate that there is no prism correction.

As you might guess, the presence of a mixed prism correction will be indicated

by both a vertical and a horizontal shift of the mires away from the lensometer

target.

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Measuring the mixed prism correction In order to measure the prism correction accurately, you will need to mark each

lens at the point through which the patient views. Be sure that the glasses are

fitted properly to the patient’s face before you make your marks. As discussed in

previous Sections, if the lens has a flat-top bifocal, you can usually assume that

this point is near the center of the seg line and just above the line.

The figure below illustrates an example of a mixed prism correction.

Let us assume that this is a right lens that we are measuring. From just a glance

at the image we know that we are dealing with a combination of base-up and

base-in prism. The intersection of the mires is above the center target of the

lensometer, indicating base-up prism. The intersection of the mires is also to the

right of the center target, indicating base-in prism. If this was a left lens, then the

horizontal prism direction would be base-out.

The amount of vertical prism can be measured by determining how far the

intersection of the mires is above the lensometer target, by means of the diopter

scale.

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In the above illustration, the intersection is 2 scale units above the target,

indicating 2 diopters of base-up prism correction.

We now rotate the scale, using the knob of the eyepiece, so that the horizontal

distance can more easily be measured.

As you can see in the figure below, the intersection lies 2 units to the right of the

target, indicating that there are 2 diopters of base-in (remember that this is a right

lens) prism correction.

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Depending upon the make of the lensometer, you will not always have to rotate

the scale in order to visualize the scale distance accurately from the target to the

intersection.

Keep in mind that the lens stage must not be moved up or down when measuring

the other lens. If both lenses show base-up prism, or if both lenses show base-

down prism, then adjust the lens stage up or down so that one of the lenses

shows no vertical prism.

If there is astigmatism present, you may have to focus “in-between” the single

line mire and the triple line mire in order to locate the intersection of the mires.

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If the axis of the astigmatism is oblique, the mires will be at an angle, making it

more difficult to estimate the distance of the intersection from the center target

along the vertical axis and the horizontal axis, as illustrated below.

Mixed prism correction that is off the scale You may encounter a mixed prism correction that is off the scale of your

lensometer, illustrated below.

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If the intersection of the mires is off the scale vertically, you will need to use a

loose prism in front of the spectacle lens with the base oriented in the opposite

direction of the vertical prism orientation in the glasses to bring the intersection

back to a position where it can be read from the scale.

Be sure to add the power of the loose prism to the scale reading power to arrive

at the correct prism power.

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If necessary, a loose prism can be used in a horizontal base orientation to bring

the intersection into the field of the horizontal scale, as illustrated below.

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Test Yourself What are are the prism corrections in the right and left lenses illustrated below?

Right lens

Left lens

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Answer: There is a prism correction in each lens. The right lens has a mixed

prism correction with 2 diopters of base-out prism and 1 diopter of base-up

prism. The left lens has 2 diopters of base-out prism and no vertical prism. The

total vertical prism correction is 1 diopter base-up OD. The total horizontal

correction is 4 diopters base-out.

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5. ADJUSTING A FRAME Frame Fitting entails selecting a ready-made product and adapting it to the

patient’s needs. By using our skills and knowledge, we can guide the patient into

buying a frame which will meet with his/her lens requirements while still satisfying

the need for looking good and feeling great! Start off with a frame that already

fits 85% correctly!

Frame fitting should proceed from front to back. Before we can begin with the

over-the-ear adjustments accurately, the frame must be aligned in both facial

planes. From top to bottom and from side to side the front should be molded to

comply to the individuals facial structure. Face form refers to the facial frame

alignment in the back and forth meridian while Pantoscopic/retroscopic angels

refer to the facial frame alignment in the up and down meridian.

HOLD ONGive some thought, prior to making any adjustments, to the way the frame will be

held while making adjustments. Select the right pliers or tool that can hold the

frame firmly while supporting the frame pieces and not damage, break or

misalign them.

Once a tool is selected, the tool should be positioned to hold the area NOT being

adjusted. Position the tool to grip both sides of the frame piece. This will ensure

that no adjustment occurs in unwanted areas.

Many parameters are considered in the selection of the proper adjusting tool,

including frame type and style, frame material, adjustment area, type of

adjustment and amount of adjustment needed.

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1. Lens Tilt, Frame Front & Nose pads The purpose to aligning the front in both meridians properly is to achieve the

closest fit possible in order to give the wearer the following:

Maximum width of visual field

Particularly in the case of stronger lens powers, close fit will allow the

exact effect of the prescribed power

Reduced spectral images due to reflections off the back surface

Visual comfort due to matched vertex distances as the eye scans from the

centre of a lens towards its outside parameters

2. Pantoscopic Angle & Vertex Distance Pantoscopic or retroscopic tilt is created at the hinge piece, at the angle where

the frame front meets the temple. Temple angles can be changed by angling the

barrel of the hinge down so the bottom of the frame front is moved "in" toward the

wearer. Bending of the barrel requires gripping and bending pliers to ensure the

proper adjustment. Recommended: 8 degrees – 12 degrees for Pantoscopic

angle and between 12mm and 16mm for Corneal vertex distance.

Incorrect front curve (Too flat)

Incorrect

Correct front curve (Slightly rounded)

Correct

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3. Frame Width

"Open temple angle" refers to the position of the temples when the temples are

not folded back on the frame. Open temple angle should be between 90 and 95

degrees. Temple angles of less than 90 degrees is adjusted by moving one or

both of the end-pieces "out" or "forward" in relation to the frame front. Open

temple angles of more than 90 degrees are corrected by adjusting one or both

end-piece positions "back in" in relation to the frame front.

Parallel temples should be considered here also. When temples are open, they

should be equal in their angle to the frame front and about parallel. Adjustments

to one or both hinge areas may be necessary to correct unequal temple angles.

The patients’ first impression of their new glasses

should not be ruined by a skewed frame. Temples

should be opened and equally angled to the front with

one another. The frame should be ready to try on.

When adjusting a frame, use pliers covered with

plastic. Metal pliers will damage the paint/metal on

the frame. Be mindful when adjusting the Pantoscopic angle of a high minus

lens as it may damage the lens. Slightly loosen the screw before the adjustment

is done. This will take the pressure of the lens – especially when working with

glass lenses.

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4. Temple Wrap

Check that the temple wrap does not apply any unwanted pressure on the

wearer’s temples. A temple wrap that is too narrow will cause the frame to slide

down the wearer’s nose, thus making it uncomfortable to wear and will produce

indentations in the wearer’s temples. This could cause an allergic reaction with

the skin and within time discolour the frame, depending on the quality of the

frame. A temple wrap that is too wide will produce an uncomfortable fitting frame.

Wrap-upChallenging frame materials, flexible plastics and new metals add to initial

adjustment difficulty and understanding. By using information from frame

manufacturers, tool suppliers, trade shows and teaching materials, frame

adjusting of new materials becomes standard.

The curved, "wrapping" aspect of new high-flex temples often takes the

adjustment of temple touch away and requires major adjustments to the area

over the ear and along the mastoid bone. Without the rigid temple, frame fit relies

heavily on proper temple bend at the crest of the ear and the appropriate amount

of touch near the mastoid bone. Be aware not to place pressure on the ear

cartilage near the crease where the back of the ear attaches to the head. Be

sure not to disregard bridge and nose pad fit. Many options are available for

bridge styles with any frame and care should be taken to choose a frame with the

proper bridge type and size.

An overall understanding of frame styles, materials and fitting parameters

ensures quick and proper adjustments to frames old and new. Combining the

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knowledge of frame styles and materials with practice of adjustment techniques

will lead to well-rounded dispensing skills and satisfied customers.

5. Temple Tips Proper temple bends will hold a frame firmly on the head without putting too

much pressure on the top and back of the patient's ears or on the bridge of the

nose. Temple adjustments vary based on temple style, material and shape.

The location of the over-the-ear bend should be placed just beyond the point

where the temples make its last contact with the top of the ear. Most effective

temple fits will achieve comfort and snugness by distributing the greatest amount

of temple surface over the greatest amount of ear surface.

Concentrate on synchronizing the bottom edge of the temple to the back of the

ear. The length to the bend should not be too short or too long. The length to the

bend should be to the top of the outer ear and the temple tips should be long

enough to hold the spectacles firmly in place so that they do not slide down the

patient’s nose.

Incorrect – no Incorrect – too much Correct – temple bend into head bend into head contours skull

Pressure

Pressure Pressure

Incorrect – bend Incorrect – bend Correct too far back too far forward

Pressure

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RIMLESSRimless frames are one of the most popular frames in today's market. This style

of frame has always been a challenge. With the introduction of stronger, more

crack resistant lenses, adjustments to three-piece mounts are a bit easier but still

put fear in some dispensers.

When using hand tools on three-piece mounts the biggest challenge is the lack of

frame area as compared to lens area. This situation makes damaging the lens by

scratching or breaking very common. Often, the use of your hands is the best

device to create the right bends.

Many three-piece mounts have very confined, hard to reach components.

Standard adjusting tools may not be the answer to these new situations. Many

frame manufactures now supply custom gripping and adjusting tools

complementary to the frame style. These tools may have interchangeable

gripping pads for different frame styles.

When adjusting rimless eyewear, first isolate the area to be adjusted. To change

the panoscopic tilt, bend the hinge area up or down while firmly holding onto the

lenses at the sleeves. Do not make adjustments by using only the lenses for

leverage. To make bridge adjustments, hold the bridge at the center and bend

the pad arms with pliers or your fingers.

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6. CONTACT LENSES

CONTACT LENSES – THE HISTORY The first plastic contact lens was introduced in the United States in 1948, but it

was not until the advent of the contour fitting principle in 1955 that lens use

among the general population began to gain wide acceptance. “Contour-Fitting”

means the use of lenses with multiple inside radii rather than a single posterior

curve, and it soon became standard practice to tailor lenses for the individual

cornea.

Today the disposable contact lens has become very popular. Some lenses are

disposed of after one day and others are disposed of weekly, bi-weekly or

monthly.

Some people prefer wearing contact lenses to glasses. One important

consideration for contact lens usage is that the decision to wear lenses is

sometimes based on therapeutic necessity rather than for cosmetic reasons.

CONTACT LENS TERM USED Contact Lenses are suitably named: they are lenses that make direct contact with

the lens of your eye! Understanding a few terms used in the eye care field can

help you understand how contact lenses work and what their benefits are.

Astigmatism: Means that your cornea is shaped more like a football than a

baseball - longer and flatter than round. If you have astigmatism, all objects are

distorted, like looking through wavy glass. Until recently, astigmatism restricted

you to glasses. Now there are even contact lenses that actually help correct the

astigmatism, called toric contact lenses.

83

Cornea: The cornea is the clear part of the eye tissue that lets light in. Contact

lenses cover part or your entire cornea.

Dry Eye Syndrome: A fairly common complaint among contact lens wearers that

is caused by insufficient tearing. Re-wetting solutions can be used throughout the

day to relieve this discomfort.

Farsightedness: If you have hyperopia, you have a more difficult time focusing

at near which results in near blurry vision. They can, however, also have a

difficult time focusing at distance. Although sometimes it can result in similar

symptoms, hyperopia is different from presbyopia.

Presbyopia is often confused with farsightedness, but the cause is actually a

hardening of the eye lens that comes with aging, making it more difficult to focus,

most commonly on close-up objects. Bifocal contact lenses are helpful to

presbyopia.

Nearsightedness: If you have myopia, you have difficulty seeing things in the

distance.

Retina: The retina receives the images that come through your lenses.

Farsightedness, nearsightedness and other vision conditions arise due to the

variations in the light reaching the retina.

SOFT CONTACT LENSES Soft contact lenses have completely revolutionized the industry and made a

world of difference to people who are tired of losing and breaking their hard

contacts.

Soft contacts now account for more than 80% of all contact lenses sold, and are

available in both disposable and extended-wear varieties. Soft contact lenses

are made of soft gel-like plastic that allows oxygen to reach the cornea. Soft

lenses are also high in water content, which enhances comfort throughout the

day.

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Soft contacts generally feel better than hard contacts and they put less pressure

on your cornea. In addition, they rarely allow dust or other particles to get trapped

between the lens and the eye, and it takes your eyes less time to get used to soft

contacts.

Soft contacts are not for everyone, though, and can be used to treat myopia and

hyperopia only.

DISPOSABLE CONTACT LENSES Disposable contact lenses have taken over the market, eliminating the need for

constant care and handling of your contacts.

Disposable lenses are available for daily wear and different periods of extended

wear, and are disposed of when their time is up.

Daily disposables are also considered healthier and safer than extended wear

contacts, since there is less chance that the lens will accumulate dust or other

particles that may lead to eye infections.

RIGID (HARD) CONTACT LENSES Rigid, or gas permeable, contact lenses have all but replaced the traditional

hard plastic contact lenses that most of us used or knew about when we were

younger.

RGP contact lenses are made of a stiff, breathable silicone that allows oxygen to

circulate in the lens and between it and your eye. This improves both the

moisture of the lens and its bacteria-fighting performance. By comparison,

traditional hard contact lenses restrict oxygen from reaching your cornea and

have become pretty much obsolete as a result.

85

RGP lenses account for about 16% of all contact lens sales. Yet they still offer

some advantages over the more popular soft contacts.

RGP contact lenses cannot rip or tear, and they generally offer clearer vision

than soft contacts. They are also much easier to handle and put it, and does not

'flop around' like soft contacts.

Finally, rigid lenses can be used to deliver a wider variety of corrective

prescriptions than soft contacts.

TORIC LENSES Toric contact lenses are a benefit to people suffering from astigmatism, a

condition in which the cornea is shaped more like a football than a baseball.

Astigmatism affects your vision by distorting the appearance of objects, as if you

were looking through wavy glass.

In the past, people with astigmatism had no choice but to wear special

prescription glasses. However, advances in the research and design have

changed all of that and lately most major manufacturers offer toric contact

lenses.

Toric refers to the special shape of the lens, which corrects the vision of people

suffering from astigmatism. Toric contacts are now widely available and can even

correct the astigmatism over time.

COLOURED CONTACT LENSES Contact lenses have become the hottest fashion accessory of the new

millennium! They are available in an amazing array of colours and tints that

change, enhance or illuminate your eyes. The colour does not affect your vision

and you can get coloured lenses with or without a prescription.

86

Coloured lenses usually come in one of two varieties - opaque lenses, in which

the centre portion of the lens is left clear; and tinted lenses in which the entire

lens is coloured.

Coloured and “fun” lenses have also become extremely popular among people

who do not require corrected vision, but enjoy the chance to experiment with their

eye colour. Even in such cases it is extremely important to make an appointment

with a professional to ensure a proper fit.

In fact, in America, the FDA recently issued a consumer advisory about coloured

contact lenses. According to the federal agency, decorative lenses can cause

87

permanent eye injuries and infections if installed or used improperly.

In particular, health experts warn against purchasing coloured non-prescription

lenses from non-professional sources, and urge people - especially teenagers -

not to trade or share contacts, since that increases the likelihood of infections.

BIFOCAL AND MULTIFOCAL CONTACT LENSES Bifocal contact lenses have become a popular way of compensating for

presbyopia - the difficulty in focusing on close objects, which affects almost

everyone to some degree after age 40.

Unlike traditional 'granny glasses' or reading glasses, bifocal and multi-focal

contacts offer a variety of ways of correcting vision for people with presbyopia.

Bifocal contact lenses utilize different viewing zones (see colour coded image

below) to achieve normal, balanced vision. The most common types of bifocal

contacts have segmented lenses, in which the top portion of the lens provides

clear distance vision while the lower portion allows for reading.

Alternatively, you may prefer to try bifocals that offer simultaneous vision

correction. This variety is constructed like a bull’s eye, with concentric rings with

differing focal capabilities.

Bifocal Contact Lens Multifocal Contact Lens

88

Bifocal and multi-focal lenses are available in soft lens and rigid formats.

However, fitting is extremely important with bifocal and multifocal contact lenses,

therefore ensure your measurements are taken carefully before attempting to fit

these lenses.

Fitting a patient with monovision contact lenses

Another alternative to typical bifocals involves monovision contact lenses, with

one eye used for distance vision and the other for reading and close objects.

89

CONTACT LENS DO’S AND DON’TS

ALWAYS NEVER

Wash your hand before touching your lenses

Clean lenses by rubbing and rinsing with fresh solution every day

Avoid using hand cream before inserting lenses

Insert lenses before applying make-up Always keep the right lens right and left lens left - even if the power is the same Never store the lenses in saline only. Use prescribed solution.

Never rinse lenses with tap water, saliva or home-made saline solution

Use solution within it’s expiry date

Replace the lens case every 3 months

Remove lenses before sleeping (unless otherwise specified)

Never wear your lenses longer than prescribed by your Optometrist

Always replace your lenses on time

Remove lenses immediately when you feel redness, pain or irritation

Replace your lenses immediately if it becomes dehydrated or chipped

While wearing lenses, keep eyes closed when using aerosol products

Always remove lenses before swimming unless otherwise specified

Consult with your Optometrist before using eye drops or ointments

Re-order contact lenses well in advance

YOUR LENS DETAILS Brand of Contact Lenses

R eye script

L eye script

Replacement Schedule

Cleaning Solution

kdjfslkjfkjefjqqfjqlqfjkfekkt

90

CONTACT LENS INSTRUCTIONS

Before handling your contact lenses, wash your hands thoroughly and dry it with

a lint-free towel. Work over a basin filled with water. Close the drain and use a

washcloth to cover the drain area.

Carefully remove the contact lens from the container. Long nails may press a

hole in the lens. Rather “pour” the lens into your hand. Rinse the lenses with

fresh solution and place the lens on the index finger of your dominant hand. If

this finger is too wet, the lens may stick to it resulting in you having difficulty

inserting the lens into your eye. To dry your finger, “scoop” the lens off your

index finger with another finger, dry the index finger with a lint free towel and

“scoop” it back again. Now, lifting your finger and looking at the lens from the

side (7), check that the lens is not turned upside down (8). Image 9 shows the

lens in the correct position.

1

987

654

32

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Another way of ensuring that the lens is not turned the wrong way round is to

loosely squeeze it between your thumb and index finger. If the lens is correct,

the ends of the lens will meet (11). If the lens is incorrectly turned, it will fold

backwards over your fingertips (10).

INSERTING THE LENS

With the ring-finger of your non-dominant hand, lift the upper eyelid (12) and hold

it tight. Ensure that you are also holding the eye lashes (13). Use the middle

finger of your dominant hand (the contact lens is on the index finger) to hold

down the bottom eyelid tightly (14).

While concentrating not to blink and looking straight ahead in the mirror (not

turning the eye up or down), place the contact lens on the eye (15). Do not blink

and look down slowly (16). Still without blinking, close your eye (17).

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12 13 14

15 16 17

10

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The contact lens has been inserted into your eye successfully (18). If you

experience discomfort, place your finger on the lens and move it into the outer

corner of your eye and back again (19). Close your eyes again and gently press

on the eye lids (20) in order to remove any air trapped between the lens and the

eye. You are now ready to wear your contact lenses for the prescribed period.

Should you experience any discomfort during the day due to wind, dust or air-

conditioned rooms, insert a drop of lens lubricant into the eye. These lubricants

are packed in individual dosages to ensure that it is sterile at all times.

You may want to use a lubricating and rewetting drop such as ReNu MultiPlus

Lubricating and Rewetting Drops just before you remove your lenses. One or two

drops in each eye will moisten the lenses and make them easier to remove.

REMOVING YOUR CONTACT LENSES

Use two or three drops of your saline solution or your lubricating/rewetting

drops in each eye 10 minutes before removing a soft contact lens. This will

rehydrate the lens so that it's not dry when you remove it.

Work over a table with a soft towel covering the top. If you work over a basin,

close the drain and use a washcloth to cover the drain area.

First take out the right lens first, then left - always.

Look up, touch the lens, and let it slide down and over to the outside corner of

the eye. The lens will bunch up, so it's easy to fold out with your fingertips and

grab out of your eye.

18 19 20

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To remove a lens that you cannot get out with your fingertips, miniature

suction cups are available at most pharmacies. These are recommended

mostly with hard contact lenses, although the cups could be useful with soft

lenses too.

CAN’T FIND YOUR CONTACT LENS?

If you have dropped a lens into the sink, plug the drain immediately and turn

off the water. Gently pat the sink and surrounding area with your fingertips to

find the lens.

Check your clothing carefully to see if the lens fell into a sleeve or got caught

in a hem or pocket.

Ask everyone who is searching for the lens to remove their shoes. Someone

might discover it by stepping on it.

Turn off the lights and search the vicinity with a flashlight or bright lamp. Get

down so you're at eye level with the floor and look for any glint from the lens.

Clean, rinse and disinfect the lens before you place it in your eye.

IPORTANT POINTS TO REMEMBER:

Get your Optometrist's OK before taking medicines or using topical eye

products, even those you buy without a prescription.

Always wash your hands before handling the lenses.

Clean lenses by rubbing and rinsing with the recommended solution or as

instructed by your optometrist.

Never re-use solution in your lens case, always use fresh solution.

Replace your contact lens case at least every 2 months.

Never use tap water, saliva or home made saline to clean or rinse lenses.

Always remove lenses before sleeping unless otherwise instructed by the

optometrist.

Never wear your lenses longer than prescribed by your optometrist.

Consult your optometrist before using any eye drops with your contact lenses.

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Insert lenses before applying make-up and remove lenses before removing

make-up.

Keep eyes closed when using aerosol products while wearing your contact

lenses.

Remember these symptoms:

R S V P – redness, secretion, vision-change and pain. If you experience any

of these, remove the lenses at once. If symptoms persist, contact us for a

check up. Your eye health as well as the integrity of the lenses will be

assessed.

Follow you prescribed wearing schedule. Begin with 2 hours on the first day,

increasing this by 2 hours a day until you reach a maximum of 10 hours. Do

not rush your wearing time! Your maximum wearing time will be determined at

your follow-up appointment.

Contact lens fitting requires a number of follow-up visits in order to finalize

your contact lens prescription. These visits are very important to ensure the

proper fit of the lens and the health of the eye.

Gas-permeable contact lenses are much simpler to insert than soft contact

lenses, but for some, more difficult to remove. Because they don't fold, you

can't really grab them with your fingertips.

Consider a thicker contact lens if thinner lenses (disposable and extended-

wear lenses) are more difficult for you to handle. It's often hard to tell if they

have folded inside out.

Clean, rinse and disinfect reusable lenses each time you remove them, even

if this is several times a day.

Clean, rinse and air-dry the lens case each time you remove the lenses. Then

put in fresh solution. Replace the lens case every six months.

Your cooperation is vital to your success in wearing contact lenses.

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CONTACT LENS INDEMNITY FORM

Each patient should sign a contact lens indemnity form before leaving the

practice with their lenses. Put the signed copy in the patient file and give a copy

to the patient.

FREQUENTLY ASKED QUESTIONS

Q. Who can wear contact lenses? A. Most individuals who require vision correction can wear contact lenses.

Technical advances in contact lens development include bi-focal contacts, daily

disposables, extended wear and frequent replacement lenses and lenses to

correct astigmatism, nearsightedness and farsightedness.

Q. Are contact lenses good for your eyes? Can they cause damage to the cornea?A. Contact lenses are a healthy vision option for many people. Only your eye

care professional can determine if contact lenses are a healthy option for you.

F O U R E Y E S O P T O M E T R I S T Contact Lens indemnity form

Date: ________________________

I, ______________________________, herewith declare that I fully understand the handling and aftercare of my contact lenses. I am also aware of the danger of over wear and the possible eye injury if I deviate from the wearing schedule and sterilizing/cleaning system.

Wearing schedule:______________________ Cleansing system:______________________

Next appointment:______________________ Instructor:_____________________________

Signed:

Patient__________________ Instructor:___________________

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When your eye care professional prescribes contact lenses and you follow all

prescribed steps for inserting, removing and caring for them, contact lenses have

proven to be a safe and effective vision correction device for millions of people.

Every contact lens wearer should see their eye care professional on a regular

basis to insure long term corneal health.

Q. How soon, or at what age, can contact lens wear begin? A. As soon as the vision correction need is identified, contact lenses can be

considered a viable option. In fact, contact lenses have frequently been used in

premature infants who often have underdeveloped retina at birth and are at risk

of blindness. With proper care and lens maintenance, infants, young children,

teens and adults of all ages can wear contacts effectively.

Q. Is it true that there are some contact lenses that can actually slow or control myopia? A. Many contact lens specialists agree that the use of Oxygen Permeable, or GP

contact lenses, that are rigid by construction, may slow or retard the progression

of myopia (nearsightedness), whereas spectacles or soft contact lenses offer no

benefit of this type. Scientific clinical studies are ongoing which will provide more

conclusive data.

Q. How do you get contact lenses that are strictly to change the appearance or color of your eyes? Is a prescription needed for these lenses?A. There are soft contact lenses available that will change the color of your eyes.

They are still considered to be a prescribed medical device that must be fit and

followed up by your eye care professional.

Q. Do I still need regular eye exams once I get contact lenses? A. Yes. The single best way to protect your vision is through regular professional

eye examinations. Eye care professionals do more than provide eye exams —

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they care for the overall health of your eyes. You should see your eye care

professional regularly.

Q. Do I need to keep my glasses once I get contact lenses? A. Yes. Though contact lenses provide benefits, you should still keep your

glasses’ prescription current. There may be days that you don’t want to wear

your lenses, or when your glasses are better suited for the situation.

Q. How often should I replace my contact lenses? A. Follow your eye care professional’s wearing and replacement schedule to

keep your lenses clean and your eyes healthy.

Q. How long can I wear my contact lenses? A. Follow your eye care professional’s wearing and replacement schedule to

keep your lenses clean and your eyes healthy.

Q. Can I swim in my contact lenses? A. You should consult your eye care professional about wearing lenses during

any water-related activities.

Q. Is it OK to play sports while wearing contact lenses? A. Contact lenses are ideal for athletes. In fact, they could give you an edge.

They offer a more natural vision correction and increase peripheral vision. And

you can quit worrying about broken frames or lenses. Plus, contact lenses don’t

fog up, slide down, or fall off. Some sports may still require protective eye gear

for safety. Ask your eye care professional if you have any questions.

Q. Can I wear makeup with my contact lenses? A. Yes. To avoid possible complications, patients who wear contact lenses

should observe the following guidelines when applying cosmetics or toiletry

products:

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Apply cologne, deodorant, and hair spray before inserting your lenses.

Wash hands thoroughly with oil-free soap prior to inserting lenses.

Put your contacts in before applying make-up.

Use water-based but water-resistant mascara that is not prone to flaking.

Two thin coats are better than one thick coat.

Use a soft pencil eyeliner rather than a liquid or powdered version that will

flake off.

Use pressed powder eye shadow rather than liquid or cream. Never use

pearlized or frosted types that may contain tinsel.

Always remove your lenses before removing makeup. Always insert your lenses

before applying eye shadow, eyeliner, and mascara.

Q. Can I wear contact lenses if I have allergies? A. Yes. Sometimes people experience discomfort during the peak of their

seasonal allergies. If that happens to you, call your eye care professional and

follow his/her recommendation. He/She may suggest you simply reduce your

wearing time or discontinue wearing your lenses until the allergy symptoms have

passed. Thoroughly and frequently cleaning your lenses may help reduce allergy

discomfort. And never use eye drops that are not made for contact lens wearers

when you are wearing your contact lenses.

Q. Can I wear someone else’s contact lenses? A. No! By using contact lenses prescribed for someone else, you risk serious eye

infection. Only wear contact lenses that have been prescribed for you. And never

allow anyone else to wear your lenses.

Q. Can a contact lens get lost behind my eye? A. No. But your contact lenses may slide under your eyelids or become

displaced. If this occurs, try looking in the direction of the lens to get it to move

back to the correct position. Soft contact lenses will tend to center automatically

on the cornea.

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Q. What if I tear or lose a contact lens? A. If you tear a lens, simply throw it away and replace it with a new one. Never

put a torn contact lens on your eye. Because your contact lenses are probably

one-day or two-week replacement lenses, they’re not as costly to replace as

lenses used to be.

Q. What if I fall asleep with my contact lenses in? A. Unless your eye care professional says it’s OK, you should always take out

your lenses before you go to sleep. If, however, you do fall asleep with them on

your eyes, remove your lenses as soon as you get up, and follow the

recommended lens cleaning and disinfecting instructions. It may be helpful to put

drops in your eyes before removing your lenses to moisturize them. If the lens is

stuck, not moving, and you are unable to remove it easily, see your patient

information booklet for how to care for a sticking (not moving) lens.