PROGRESSIVE PROGRESSIVE ADDITION LENS:ADDITION LENS: OPTICS AND DESIGNOPTICS AND DESIGNSHRESTHA GS, M.Optom

Presbyopia correction PALs Enhanced near vision Bifocals Trifocals SV (readers):

full aperture half-eyes

RANGE OF CLEAR VISION

Single vision

Bifocal

Progressive

0.33 0.50 1.00 2.00 5.00

NEAR INTERMEDIATE DISTANCE

NEAR INTERMEDIATE DISTANCE

NEAR INTERMEDIATE DISTANCE

PURPOSE Understand experience with current

correction Highlight limitations of current correction Explain feature/benefits Refer to “change in vision” when refitting

into different design Listen to the wearer’s needs Restate the wearer’s needs (avoid technical

jargon) Make the recommendation

What are progressive addition lens ?

1

Progressive Addition LensesProgressive Addition Lenses

What are progressive addition lenses?A lens designed forpresbyopes with power gradually increasing from the distance zone, through a progression to the near zone.

Physiological Considerations

Distance

Intermediate Near

Typical dioptric power (D) for clear viewing of objects

The usable field of view is comprised of head and eye movements as shown here for the horizontal plane.

Usable Field of View

Eye rotation

Head movement

PALs design and personal movement characteristics

Binocular Vision

Binocular vision:

As the patient’s gaze is lowered for near objects, the eyes converge to maintain a single binocular image. The progressive lenses should ensure that this is maintained for different object distances from the eyes, as illustrated by the lines.

Peripheral (Extra-Foveal) VisionPeripheral

vision:The PAL design should ensure

that *objects in the periphery of

the visual field are easily fused.

**The distribution of prism in each lens should also be balanced for

binocular viewing.

***Corresponding areas in the two

lenses should provide a similar

level of vision.

Why Use PALs?

Uninterrupted vision from distance to near

No visible line

No jump in vision from distance to near

Better vision as intermediate is clear

Looks like single vision Lighter/thinner than SV Looks better

More natural vision More visual comfort Confidence in mobility

Feature Benefit

Intermediate Vision

Intermediate vision:(a) Poor head position as a consequence of the eyes searching for the best focus in the bifocal’s limited range of intermediate clear vision. (b) Using the intermediate portion of a PAL enables more natural head position.

(a) Bifocal

(b) PAL

Why Use Progressive Lenses?

Bifocal lens Progressive lens

The bifocal lens (left) can disrupt the patient’s view with visual disturbances (arrows) when the eye crosses the boundary of the near seg. The progressive lens (right) has no such problem and enables a smooth transition between different reading distances.

PAL references

How a progressive addition lens works?

Invariably follow the traditional lens optics Power in the midline follows the same

distance prescription as addition increases below until desired add is reached

For the most of the lenses, this addition power is reached at a point 10-16mm below and 2.0-2.5mm nasal from distance optic centre

Width Width =

Lens design + Add

Astigmatic Astigmatic errorerror =

Width of near area + add

Progressive Lens Design - Optics

Distance Zone

Near Zone

Umbilical line

Intermediate

Zone

Lens Radius Changes Along Lens Radius Changes Along Umbilical LineUmbilical Line

Principal parameter : Size of distance & near area

Type and intensity of aberration

Depth & usable width of corridor

Design in PAL’S : Hard design Soft design Symmetrical design Asymmetrical design Mono design Multi design Prescription based design

Progressive Lens Design2. Hard Vs Soft Lens Design

Hard Soft

Hard design Regular distance single

vision Spherical distance zone Wide distance & near zone Narrow & short intermediate

corridor Rapid increase in unwanted

astigmatism

Advantages

Large distance & near area free from astigmatism

More accessible with downward rotation of eye

Wider near zone even at high Rx Disadvantages : High intensity aberration at periphery Distortion for longer and more difficult

period of adaptation Swim effect

Soft design : Aspheric upper halves Narrower distance & near

zone Wide & large intermediate

corridor Gradual increase in

unwanted astigmatism

Width of Far Vision (+4mm):0.5 [D]- 16.2 mm

1.0 [D]- Unlimited

Max Cylinder [D]- Nasal: 1.5[D]

Max Cylinder [D]- Temporal: 1.5 [D]

Width of Corridor (-6mm):

1.0[D]- 9 mm

Length of corridor:14.2 mm

Minimum fitting:19 mm

Width of near Vision (-18 mm):1.0[D]- 21.63 mm

Soft Design

Advantages Decreases intensity aberration at

periphery Easier, more rapid adaptation Less distortion of peripheral viewing Reduce swim effect Disadvantages : smaller field at sharp vision Need dropping of eye farther near to

read

Indication for selection

Hard design : Previous successful hard lens

wearers People who do a lot of reading Soft design : Young presbyopes Active outdoor profession Professional driver

Symmetrical design :

Add is straight down from distance optical center

No right & left lenses Required rotation to

achieve desired inset for near (9 degree)

Advantages : We can give the inset according to

patient Disadvantages : As the wearers looks to the side

they will experience different power & differential prism

Asymmetrical design : Lenses have pre-

set inset for near

Different lenses for right & left

Progressive Lens Design3. Symmetrical Vs Asymmetrical

Symmetrical PAL - same lens design is rotated to fit the other eye

Asymmetrical PAL - each eye has a different lens

Advantages : This will not produces experience

of different power when patient looks to a side

Disadvantages : Fixed inset may not match with

patient’s required inset

Mono design : Describe range of power for a

given design It classify hard & soft It describe the characteristics of

progressive zone Maintain design principles

throughout the range of addition

Multi design : According to add power lens

design changes It start from soft design for low add

power & as the add power increase it will turn to hard design lens

1.50 Add Design1.50 Add Design

2.00 Add Design2.00 Add Design 2.50 Add 2.50 Add DesignDesign

Prescription base design : Result of years of Vision Research Dedicated design for every Base and Add Design by Base : different designs for

Hyperopes, Emmetropes and Myopes (FOV & Magn.)

Design by Add: effective near zone sizes change as the add increases

Near inset position varies relative to level of Presbyopia / reading distance

Corridor length also varies relative to both Base and Add

Incorporating Single vision aspheric design in to the PALs Aspheric advantage Flat, thin, lighter Earlier front surface aspheric

design Back surface Aspheric design Bi-aspheric design

USE OF CONTOUR PLOT TO EVALUATE PROGRESSIVE LENSES Distortion of grid patterns viewed

through the lenses Visual acuity attainable at different

portions The amount of vertical imbalance

at paired peripheral pointsAreas of equal cylinder power plotted with a connecting line- Isocylinder line

Equal spherical equivalent powers-

Lens Design Selection Consider how the wearer uses their lenses

for most wearers a good modern progressive lens design is the best solution

but not all designs provide wide fields of view at distance, intermediate and near

consider the design that will suit the wearer general purpose : balanced fields of view mainly for reading : wide near visual fields mainly for computer : wide intermediate visual fields

• Contour Plot Description• Design Technology• Visual Boundaries• Performance Implications• Growing Product Category

Knowledge continues to Evolve

Summary

Disadvantage of PALs Straight line appears curved

More adaptation Decreased width at intermediate

and near Limited lateral movement

Increase in eye and head movement

Eye must be dropped a longer distance

Rodenstock Perfect read R For half eye reading glass users

who need trifocal Ordinary PALs to much peripheral

aberration occurs Use of full lens useful area Near power is the reference power Near IPD is the measured

estimation Power of the lens starts out with

intermediate prescription

Varilux readable

Full working field enjoy as single vision lens for intermediate and near

Much clearer intermediate which can’t be attained by single vision lens

INTERMEDIATE

+0.75

+0.75

12mm

4mm

28 mm

Cosmolit P Aspheric thin design

-0.75D

Add

20mm

10mm

Overview Electricians, plumber,

painter, pharmacists, librarians

41mmAdd-0.50

9mm

Technica Soft design of 1.00cyl max

Distance

Intermediate

Near

MRP: 50% 0f add

Some of the common Progressive lens from essilor Espace: affordable price and field

of vision for all distances Adaptor; soft design, good

distance, optimized intermediate and wide near vision area

Varilux comfort: sharp and natural comfortable vision, good distance, optimized intermediate and adequate near vision area

Varilux comfort 1.6: Thinner and lighter than normal progressive

Varilux panamic: wide field of vision for all distances

Varilux panamic 1.6: Nicon Presio: wider intermediate and

near zones, for small size frames Comfort transition: progressive

+photochromic Nikon web.lens: enhanced near vision

for computer savvy presbyopes

Sola Progressive Solamax: highest reading area,

Spectralite; thinnest of all Percepta: wider clear vison for all XL gold: intermediate for sports and arm

length activity Graduate: first time wearer, wide

distance and near

XL

Graduate

Computer lens

Upper portion formid-rangedistances

Lower portion hasreading Rx

Power variessmoothly fromtop to bottom

12 mm power transitionzone

Mid-range

Near

Access uses a unique aspheric surface:

ACCESSTM

Breaks the Mid-Range BarrierBreaks the Mid-Range Barrier Access provides

Extended range Wider breadth of field Mid-range vision is as wide as close-up vision Continuous vision throughout the lens Ease of use

mc compared to Adult Progressive Lenses

Addition Power Plot

mc Myopia ControlStandard Adult Progressive

Short Corridor Adult Progressive

Eye tracking

R1Far Zone

RnProgressive Zone

R2Near Zone

Controlling the distortion is the key to

the ultimate progressive lens

Topographic Map

Minimizing Distortions

The technology that enables us to design progressive lensesthrough an exact simulation of the natural human eye view.

Eye Point Technology

The optical power is created by 3 parameters: thickness, index and curvatures

The surface of the lens is scanned by a 3D measuring system, mapping

the curvatures of the lens.

Eye Point Technology

The surface data & a highly advanced mathematical algorithm are the basis to Shamir's Eye-Point Technology™, which takes into account numerous parameters:

1. Lens index refraction

2. Lens prescription

3. Lens center thickness

4. Distance from the eye to the back vertex of the lens

5. Distance from the lens to the object

6. Object's angular position in the eye's field of vision

7. Pantoscopic tilt of the frame

8. Pupil distance

9. Thickness reduction prism, and more.

By taking all of these parameters into consideration, Shamir's Eye-Point Technology™ enabled the creation of the perfect progressive lens.

Eye Point Technology

Visual Simulator

Panamic Rodenstock Life 2 Hoya GP Wide Zeiss Gradal Top Sola Max

Analyzed by Rotlex Class I on a random lens

Comparison

Sola MaxPanamic Rodenstock Life 2 Hoya GP Wide Zeiss Gradal Top

Comparison

Comparison

Thank you