overview of contact lenses

04/04/2012 Overview of contact lenses

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Official reprint from UpToDate® www.uptodate.com

©2012 UpToDate®

AuthorMichael J Lipson, OD, FAAO

Section EditorJonathan Trobe, MD

Deputy EditorH Nancy Sokol, MD

Overview of contact lenses

Disclosures

All topics are updated as new evidence becomes available and our peer review process is complete.Literature review current through: thg 2 2012. | This topic last updated: thg 11 9, 2011.

INTRODUCTION — An estimated 40 million people in the United States wear contact lenses, with

approximately 38 million soft lens wearers and 2 million rigid gas-permeable lens wearers [1]. Surveys show

that in recent years the number of new contact lens users is almost equal to the number of contact lens

failures.

Contact lenses may be categorized by their compositional material, wearing schedule, disposal schedule,

permeability, water content, and type of correction (table 1). With many new lens types available, there are

alternatives to help most patients achieve comfortable lens wear with clear vision. New types of contact

lenses are continually being introduced with the intent to decrease risks of infection, inflammation, and

conjunctival trauma while maximizing vision correction and convenience of use [2].

The types of available contact lenses, indications for their use, and appropriate care to decrease the risk of

infection or trauma will be reviewed here. The complications with contact lens use are discussed separately.

(See "Complications of contact lenses".)

HYDROPHILIC/SOFT LENSES — Soft lenses account for more than 90 percent of prescribed contact lenses

in the United States (table 1) and worldwide (table 2) [3,4].

Soft lenses are used to correct a variety of refractive errors, including myopia, hyperopia, astigmatism (toric

lenses), and presbyopia (multifocal lenses). Not every prescription is available in every material or brand.

Certain refractive errors, caused by keratoconus or other corneal distortions, may not be correctable with

soft lenses.

Soft lenses are generally quite comfortable and easier to adapt to than rigid lenses. Patients wearing soft

lenses need regular follow-up care and must be compliant with lens care regimens to avoid serious eye

problems. (See 'Guidelines for prevention of infectious keratitis' below.) Patients who discontinue wearing

lenses most commonly complain of lens awareness or dry feeling while wearing lenses. Other reasons include

inadequate visual acuity, allergic reactions, and difficulty handling lenses [5].

Composition — Soft lenses are made of various plastic polymers that absorb water (hydrophilic). These

materials differ in terms of oxygen permeability (expressed in Dk units, where D stands for diffusion and k for

solubility), water content (varying between 20 and 70 percent water by weight), surface quality

(wettability), ultraviolet absorption, and structural consistency (stiffness or modulus). The US Food and Drug

Administration (FDA) has developed a system for classifying soft lenses (table 3).

All soft lenses absorb water, as well as a variety of other substances: chemicals in contact lens solutions,

tear secretions, makeup, and airborne chemicals or vapors. Oily substances from the eyelids or facial creams

that come in contact with the lens can coat the lens surface.

Prior to 1996, the polymer in all soft lenses was primarily 2-hydroxyethyl methacrylate (HEMA)–based, which

is still used in several current lenses. Polymers with silicone hydrogel (SH), which are more highly oxygen

permeable, were introduced in 1999 and are now more common in newer types of lenses [1]. Lenses with

higher oxygen permeability are generally considered a healthier option [6], although case control studies did

not demonstrate that SH lenses decreased the risk of microbial keratitis [7] or of nonulcerative contact lens–

related disorders seen in an emergency setting [8].



Physical characteristics of different SH lenses are detailed in a table (table 4). Dk/t is a measure specific to

the individual lens, rather than its material, and refers to the oxygen permeability (Dk) of the material

normalized for the thickness of the lens (t). The higher the Dk/t value, the more breathable the lens. Patients

using higher Dk/t lenses develop less corneal edema during all-day or overnight wear, compared to HEMA-

based lenses [6]. Other material characteristics include water content, surface quality (wettability),

ultraviolet absorption, and modulus (stiffness). The higher modulus lenses will feel stiffer, and lower modulus

lenses floppier, when handled.

Soft lens materials provide a good medium for microbial growth. Additionally, if patients are not compliant

with care techniques, red-eye reactions, discomfort and allergic reactions can occur. Proper disinfection

procedures are essential. (See 'Lens care and lens solutions' below.)

Other sources of eye irritation are lens deposits (chemical or mechanical), foreign bodies trapped under the

contact lens, and allergic reactions to preservatives in the care solutions. (See "Complications of contact

lenses".)

Length of wear — The absorption characteristics of soft lenses and their tendency to accumulate surface

deposits can affect oxygen permeability and surface quality. Therefore, soft lenses allow only a limited time

of safe and healthy usage and should be worn and disposed of on an individually prescribed schedule.

One day lenses — These lenses are designed for one day wear and are dispensed in a large supply (30 or

90 pair). They are ideal for people who want to wear contact lenses intermittently, for those who place

convenience as a high priority, and for those who have sensitivity to disinfecting solutions since they do not

require use of disinfecting solutions.

Two week disposable — These lenses are the most commonly prescribed in the United States and are

worn for a maximum of two weeks. Most should be removed each night and cleaned and disinfected, but

some have FDA approval for six days and nights of continuous wear.

Monthly disposable — Most of these lenses are also worn during the day and removed each night,

although some have approval for 30 days of continuous wear.

Quarterly disposable — These lenses, designed to be replaced every three months, are generally

custom-made lenses for high prescriptions.

Special use soft lenses

Tinted soft lenses — Soft lenses can be tinted for cosmetic, therapeutic or prosthetic purposes.

Cosmetic tints — Many soft lenses can be made in a variety of colors. The tints may be transparent to

enhance natural eye color or can be opaque to dramatically change the color of the iris.

Therapeutic tints — These special tints are used for highly light-sensitive patients or to enhance color

perception in patients with color deficiencies. Though these lenses do not fully compensate for color

blindness, they are tinted red and worn to help color-deficient patients identify reds and greens more

readily.

Prosthetic tints — Soft lenses can be tinted or hand-painted to improve cosmesis in patients with

scarred corneas or to create an artificial pupil in patients with aniridia, albinism or damaged/distorted

pupils.

Bandage lenses — Soft lenses are used as bandage lenses in cases of corneal laceration, corneal

exposure injury, and during the healing phase after some ocular surgery such as photorefractive keratectomy

(PRK).

Piggyback fitting — In cases of highly irregular corneal curvature, as in keratoconus, a soft lens is placed

on the cornea and a rigid contact lens is placed over it. The soft lens provides a more regular surface for the

rigid gas-permeable (RGP) lens to ride upon and also acts to protect the cornea from irritation due to

excessive movement of the RGP lens.

RIGID GAS-PERMEABLE LENSES — Rigid gas-permeable (RGP) contact lenses hold a specific shape although



they do have a small amount of flexure. Compared to soft contact lenses, RGP lenses generally provide better

visual acuity and are more durable but require longer periods for adaptation. Most wearers can achieve

excellent comfort after four to seven days of wear. RGP lenses are generally replaced after two to three

years of use.

Prior to the development of RGP lenses, "hard" lenses were made of a plastic material,

polymethylmethacrylate (PMMA). This material provided no oxygen permeability and depended on tear

circulation to provide oxygen to the cornea. With the development of RGP lenses, PMMA materials are now

rarely used.

Because of their rigidity, RGP lenses are often used to achieve optimal visual acuity in patients who have not

had satisfactory acuity with soft lenses. RGP lenses are also generally better for those who have some

degree of "dry eyes." RGP lenses are also used for overnight corneal reshaping to improve daytime acuity

(orthokeratology) [9-11].

RGP lenses comprise about 5 to 10 percent of all contact lens fits in the US, including 1 percent for overnight

corneal reshaping [1]. There are more than 40 different RGP materials used today. As with soft lens

materials, each type of RGP lens has unique characteristics in regards to wettability, oxygen transmission,

and flexure [5]. Many of these lenses are more gas permeable than soft lenses.

Most RGP wearers use their lenses during the day. Some lenses are approved by the US Food and Drug

Administration for one week of continuous wear and at least one brand has approval for 30 days of

continuous wear.

RGP lenses are ordered by the eye care practitioner and made on a custom basis by an RGP lab. Providers

can specify various parameters to optimize fit and comfort including diameter, base curve, power, peripheral

curves, thickness, edge design, optical zone, as well as material and color.

Within the last 15 years, computer-guided lathes have been developed that allow manufacture of highly-

customized lenses. RGP lenses can be ordered to fit the inter-palpebral opening (7 to 9 mm), the corneal

diameter (10.0 to 11.5 mm), the corneoscleral area (12 to 15 mm), or the sclera (16 to 24 mm).

Custom RGP designs may be the only vision correction option for patients with irregular corneal topography

who are not correctable with soft lenses or spectacles. Specialty RGP designs include:

Reverse geometry — steeper curvature peripherally than centrally

Quadrant specific curves — different curves in each quadrant of the lens

Toric/bitoric — different curves horizontally versus vertically (on front and/or back surface)

Aspheric curves — placed on front or back surface

Multifocal lenses — eg, aspheric, segmented, concentric

Corneal reshaping — reverse geometry lenses of custom or proprietary design to temporarily change

the corneal curvature to improve unaided acuity

Hybrid contact lenses — Hybrid contact lenses have an RGP central portion fused to a peripheral soft skirt.

The first lens of this type (SoftPerm) was made of very low permeability materials and had limited

parameters. A newer version of this innovative design (Synergeyes/Duette) is comprised of more permeable

materials (both central RGP and peripheral soft) and with various parameters to allow fitting over a large

range of unique corneal shapes [12,13]. These lenses are worn during the day and disposed of after six

months of use.

The various designs of hybrid lenses can be made to correct for myopia, hyperopia, astigmatism, presbyopia

(multifocal design), keratoconus, post-surgical eyes, and other irregular astigmatism cases.

Advantages of hybrid lenses are excellent acuity, greater comfort compared with RGP lenses, and a wide

range of parameters and designs. Disadvantages of hybrid lenses are more difficult insertion and removal, and

higher costs than other lenses.

LENS CARE AND LENS SOLUTIONS

Caution in contact lens wear — Contact lens wear and/or lens care solutions can provoke many eye

reactions. Infection risk can be minimized by following proper procedures for contact lens care.



Common problems include [7,14]:

Redness

Itching

Dryness

Allergic reactions

Conjunctivitis (microbial, mechanical, allergic or inflammatory) [14]

CLARE (contact lens-induced acute red eye)

CLARE refers to a sudden red eye reaction in a contact lens wearer of unknown etiology. Possible causes are

lens deposits, low grade infection, chemical sensitivity to solution or external chemical contamination of the

contact lens.

Patients experiencing minor redness or itching without pain or blurred vision should be treated initially with

removal of contact lenses and lubricating eye drops (artificial tears or over-the-counter antihistamine drops).

They should be advised to report any increase in severity of symptoms or development of blurred vision or

pain. After resolution of minor irritations, future episodes may be prevented by changing the replacement

schedule, reducing wearing time, or a change in the lens type or disinfection regimen.

Consultation with the eye care provider should be arranged promptly if patients experience blurred vision,

pain, or photophobia. More serious conditions associated with contact lenses include corneal ulcers [7],

corneal abrasions, and infectious keratitis. (See "Complications of contact lenses".)

Solutions are used to clean and disinfect contact lenses. Reports of serious infections have been related to

contaminated lens cases and inadequate patient disinfectant technique [15]. (See "Free living amebas",

section on 'Amebic keratitis' and "Clinical manifestations and diagnosis of Fusarium infection", section on

'Keratitis'.)

Soft lens solutions

Multipurpose solutions — Multipurpose solutions (MPS) are the most commonly used, accounting for 89

percent of solutions used in the US versus 11 percent for peroxide systems in 2008 [1]. MPS are intended to

be "all-in-one" solutions that are used to rinse, clean, disinfect, and store lenses during their overnight

soaking. Success with MPS depends on patient compliance with directions, particularly in regard to sufficient

rinsing or, preferably, using a rub technique to achieve adequate disinfection [16,17]. Individual patient

tolerance is variable, and some find that multipurpose solutions provoke an allergic or toxic reaction when

exposed to the eye. Available multipurpose solutions in the US are shown in a table (table 5). Generic

versions are also available at various retailers.

While MPS offer several conveniences compared to other contact lens solutions (ready availability, one

bottle, ease for travel) MPS are also more likely to cause allergic or sensitivity reactions, and corneal staining

is more prevalent than with peroxide systems.

Peroxide systems — Peroxide systems have gained in popularity over the last few years. They use

hydrogen peroxide to disinfect and passively oxidize surface deposits. These systems require that the

peroxide solution be "neutralized" prior to lens use, and different techniques (one or two-step) are used for

accomplishing this. Commercially available peroxide systems in the US are shown in a table (table 5).

Peroxide disinfection, compared to MPS, provides no direct exposure to preservatives and there is a lower

likelihood of sensitivity reactions. Lens cleaning is passive, by oxidation, and there is less risk for

noncompliance resulting in infection. However, peroxide systems lack the convenience factors of MPS, are

more difficult to travel with, and pose the potential for irritation from accidental exposure to non-neutralized

solution.

Guidelines for prevention of infectious keratitis — Following national and international reports of

Acanthamoeba keratitis and Fusarium keratitis, the US Food and Drug Administration (FDA) reviewed proper

care of contact lenses. Citing the risk of eye infections and corneal ulcers, with the potential to cause

blindness, the FDA has issued recommendations and guidelines for the safe use of contact lenses and

associated care products [18]. These recommendations follow:



Always wash your hands before handling contact lenses to reduce the chance of getting an infection.

Remove the lenses immediately and consult your eye care professional if your eyes become red,

irritated, or your vision changes.

Always follow the directions of your eye care professional and all labeling instruction for proper use of

contact lenses and lens care products.

Use contact lens products and solutions recommended by your eye care professional.

Do not use contact lens solutions that have gone beyond the expiration or discard date.

Rub and rinse your contact lenses as directed by your eye care professional.

Clean and disinfect your lenses properly following all labeling instructions provided with your lens care

products.

Do not "top-off" the solutions in your case. Always discard all of the left over contact lens solution

after each use. Never reuse any lens solution.

Never use non-sterile water (distilled water, tap water or any homemade saline solution). Exposure of

contact lenses to water has been associated with Acanthamoeba keratitis, a corneal infection that is

resistant to treatment and cure.

Do not put your lenses in your mouth to wet them. Saliva is not a sterile solution.

Clean, rinse, and air-dry your lens case each time lenses are removed. You may want to flip over your

lens case while air drying so excess solution may drain out of the case. Contact lens cases can be a

source of bacterial growth.

Replace your contact lens storage case every three to six months.

Do not transfer contact lens solutions into smaller travel size containers. This can affect the sterility of

the solution which can lead to an eye infection. Transferring solutions into smaller size containers may

also leave consumers open to accidentally using a solution not intended for the eyes.

A synopsis of these recommendations is presented in a table (table 6).

Rigid gas-permeable solutions — Solutions to be used with RGP lenses vary in viscosity, wetting agent,

and preservatives. One to three bottles contain solutions designed for wetting/conditioning, disinfecting, and

cleaning. Available solutions in the US are shown in a table (table 5).

Lubricating drops — There are numerous brands of drops that are designed to be used with contact lenses

as lubricants at frequencies varying from once per day to hourly. These may be labeled as "contact lens

drops," artificial tears, or lubricating drops. Available lubricants differ in their viscosity and whether or not

they are preserved, and individual patient preference and tolerance will determine which is most acceptable.

Compatibility with patient's eyes, individual contact lens brand, and other solutions patients use are also

factors.

CONTACT LENS FITTING — Contact lens fitting should be done by experienced clinicians who may be

optometrists or ophthalmologists. A thorough pre-fitting evaluation can identify risk factors and target the

best lens and lens care combination to provide long-term comfort, good vision, and easy maintenance.

A thorough pre-fitting evaluation should include:

Refraction and visual acuity

Keratometry

Corneal topography

Biomicroscopic evaluation of the cornea, conjunctiva, and eyelids

Empirical and/or diagnostic fitting

Instruction about insertion/removal, lens care, and solutions



After initial dispensing, follow-up evaluations should include:

Biomicroscopic evaluation of the cornea, conjunctiva, and eyelids with and without contact lenses in

place

Visual acuity

Review of care, handling, and disinfection procedures

Follow-up frequency — New contact lens wearers should generally be seen within the first week, at one

month, six months, and annually thereafter. This frequency may vary with the type of lens, wearing

schedule, and condition being treated.

INSERTION AND REMOVAL TECHNIQUE — Insertion of all types of lenses involves, with clean hands,

placing the prepared lens directly on the center of the cornea while holding the lids and lashes to create an

opening large enough to clear the diameter of the lens.

Removal techniques vary with the lens type:

Soft lenses are removed by pinching the edges of the lens at the four and eight o'clock positions with

the thumb and index finger while holding the upper lid out of the way. Inserting a drop of wetting

solution or artificial tears makes removal easier.

If the lens is not readily removed, it is possible the lens is in the eye but not on center. The most likely place

to find the dislocated lens is under the upper lid (usually folded). To check for this, have the patient look

straight down while holding the upper lid up as high as possible. If found, the lens can be pinched out from

there. It may be necessary to evert the lid to find a lens that has adhered to the inner surface of the upper

lid.

Rigid gas-permeable lenses can be removed with a rubbery contact lens removal tool (suction cup) or

by manipulating the upper and lower lid simultaneously together against the edges of the lens. If an

RGP lens is off-center, it is best to try to manipulate the lens position through the closed lids to a

position of easy access, usually the temporal sclera, and then use the suction cup device.

Hybrid lenses are removed similar to soft lenses, except that the area of pinching must be smaller, at

the edge of the soft portion of the lens. Pinch the soft portion with both fingers at the six o'clock

position. With this lens, it is critical that the upper lid be held away from the surface of the lens to

allow for removal. Again, lubricating drops inserted in the eye can help remove a lens that is not coming

out easily.

FUTURE DEVELOPMENTS — Investigation is ongoing to develop new designs, materials, and applications for

contact lenses.

Drug delivery systems — Lenses impregnated with drugs for slow sustained release are being evaluated

for anti-infective, anti- inflammatory, and pressure-lowering indications [19-21].

Newer coatings — Different coatings are under investigation to make lenses more resistant to bacterial

adhesion and to minimize mucous or protein deposits [22,23].

Multifocal lenses — New lens designs in various materials aim to improve acuity for distance and near

vision [24,25].

Aberration-correcting contact lens — Based on wavefront refractive and corneal analysis, these lenses

are wavefront-generated to provide a customized correction and improve visual acuity over traditional

optics [26-28].

SUMMARY AND RECOMMENDATIONS

Contact lenses may be categorized by their compositional material, wearing schedule, disposal

schedule, permeability, water content, and type of correction (table 1). (See 'Introduction' above.)



Soft lenses can be classified by a number of properties, including oxygen permeability, water content,

and structural consistency (table 3). Silicon hydrogel lenses, with increased oxygen permeability, are

often considered preferable. (See 'Hydrophilic/soft lenses' above.)

Rigid gas-permeable (RGP) contact lenses hold a specific shape although they do have a small amount

of flexure. Compared to soft contact lenses, RGP lenses generally provide better visual acuity and are

more durable but require longer periods for adaptation. (See 'Rigid gas-permeable lenses' above.)

Multipurpose solutions are the most commonly used solutions in the United States to rinse, clean,

disinfect, and store lenses during their overnight soaking. Compared to other solutions, MPS are more

convenient but more likely to cause allergic or sensitivity reactions. Peroxide disinfection systems

provides no direct exposure to preservatives, though are somewhat less convenient. (See 'Multipurpose

solutions' above and 'Peroxide systems' above.)

Proper use of contact lenses and hygienic recommendations were issued in a guideline from the US

Food and Drug Administration, after review of the factors contributing to outbreaks of Acanthamoeba

keratitis and Fusarium keratitis. These recommendations include hand washing, discarding outdated

solutions, following instructions for disinfection, only using manufacture-prepared solutions in their

original bottles, not saliva, as a lubricant, cleaning cases and replacing them every three to six months.

(See 'Guidelines for prevention of infectious keratitis' above.)

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REFERENCES

1. Nichols J. Contact Lenses 2008. Contact Lens Spectrum 2009; 1:24. Available at:http://www.clspectrum.com/article.aspx?article=102473 (Accessed on November 01, 2011).

2. Foulks GN. Prolonging contact lens wear and making contact lens wear safer. Am J Ophthalmol 2006;141:369.

3. Mack C. Contact Lenses 2007: A look back at contact lens events of 2007 including prescribing trends,product recalls and launches, compliance issue, mergers and corneal staining. Contact Lens Spectrum2008. Available at: http://www.clspectrum.com/article.aspx?article=101240 (Accessed on November 01,2011).

4. Morgan PB, Woods CA, Knajian R, et al. International Contact Lens Prescribing in 2007: Our annualreview of international prescribing trends reports on close to 20,000 prospectively conducted fits in 27countries. Contact Lens Spectrum 2008. Available at: http://www.clspectrum.com/article.aspx?article=101241 (Accessed on November 01, 2011).

5. Soft Contact Lenses: Hydrogel and Silicone Hydrogel Lens General Considerations. Contact LensSpectrum 2008. Available at: http://www.clspectrum.com/article.aspx?article=&loc=archive\2008\july\supplements\cls_class\cls_july_class_suppl_a02.html (Accessed onNovember 01, 2011).

6. Stern J, Wong R, Naduvilath TJ, et al. Comparison of the performance of 6- or 30-night extended wearschedules with silicone hydrogel lenses over 3 years. Optom Vis Sci 2004; 81:398.

7. Dart JK, Radford CF, Minassian D, et al. Risk factors for microbial keratitis with contemporary contactlenses: a case-control study. Ophthalmology 2008; 115:1647.

8. Radford CF, Minassian D, Dart JK, et al. Risk factors for nonulcerative contact lens complications in anophthalmic accident and emergency department: a case-control study. Ophthalmology 2009; 116:385.

9. Jupiter DG, Katz HR. Management of irregular astigmatism with rigid gas permeable contact lenses. CLAOJ 2000; 26:14.

10. Swarbrick HA, Wong G, O'Leary DJ. Corneal response to orthokeratology. Optom Vis Sci 1998; 75:791.

11. Lipson MJ, Sugar A, Musch DC. Overnight corneal reshaping versus soft disposable contact lenses:vision-related quality-of-life differences from a randomized clinical trial. Optom Vis Sci 2005; 82:886.

12. Lipson MJ, Musch DC. Synergeyes versus soft toric lenses: vision-related quality of life. Optom Vis Sci2007; 84:593.



13. Nau AC. A comparison of synergeyes versus traditional rigid gas permeable lens designs for patients withirregular corneas. Eye Contact Lens 2008; 34:198.

14. Lemp MA. Contact lenses and allergy. Curr Opin Allergy Clin Immunol 2008; 8:457.

15. Patel A, Hammersmith K. Contact lens-related microbial keratitis: recent outbreaks. Curr OpinOphthalmol 2008; 19:302.

16. Koffler BH, Karpecki PM. Positive aspects of the use of multipurpose disinfection solutions. ArchOphthalmol 2009; 127:1540.

17. Cohen EJ. Contact lens solutions: part of the problem. Arch Ophthalmol 2009; 127:1544.

18. FDA Website. Available at: www.fda.gov/cdrh/contactlenses/lenslist.html (Accessed on November 01,2011).

19. Hiratani H, Alvarez-Lorenzo C. The nature of backbone monomers determines the performance ofimprinted soft contact lenses as timolol drug delivery systems. Biomaterials 2004; 25:1105.

20. Gulsen D, Chauhan A. Ophthalmic drug delivery through contact lenses. Invest Ophthalmol Vis Sci 2004;45:2342.

21. Ciolino JB, Hoare TR, Iwata NG, et al. A drug-eluting contact lens. Invest Ophthalmol Vis Sci 2009;50:3346.

22. Valint, PL, et al. Plasma Surface Treatment of Slicone Hydrogel Contact Lenses with a Flexible CarbonCoating. US Patent # 6,213,604 B1 April 10, 2001.

23. Carney et al Medical Devices Having Antimicrobial coatings. Theron US Patent application # 10/722,256July 15, 2004.

24. Guillon M, Maissa C, Cooper P, et al. Visual performance of a multi-zone bifocal and a progressivemultifocal contact lens. CLAO J 2002; 28:88.

25. Pujol J, Gispets J, Arjona M. Optical performance in eyes wearing two multifocal contact lens designs.Ophthalmic Physiol Opt 2003; 23:347.

26. Guirao A, Porter J, Williams DR, Cox IG. Calculated impact of higher-order monochromatic aberrations onretinal image quality in a population of human eyes. J Opt Soc Am A Opt Image Sci Vis 2002; 19:620.

27. de Brabander J, Chateau N, Marin G, et al. Simulated optical performance of custom wavefront softcontact lenses for keratoconus. Optom Vis Sci 2003; 80:637.

28. Thibos LN, Cheng X, Bradley A. Design principles and limitations of wave-front guided contact lenses.Eye Contact Lens 2003; 29:S167.

Topic 6906 Version 4.0



GRAPHICS

2010 US soft lens market

By lens material Percent

Silicone hydrogel 66

Soft hydrogel 25

RGP 8

Hybrid 1

By lens type Percent

Soft spherical 53

Soft toric 21

Soft multifocal 11

RGP spherical 6

RGP multifocal 1

RGP toric 1

Ortho-K 1

By disposal schedule Percent

Daily 13

Weekly 2

Two weeks 36

One month 42

Three months 4

Annual 3

RGP: rigid gas permeable. Data from: Nichols JJ, et al. Contact Lenses 2010. Contact Lens Spectrum 2011.

Available at: www.clspectrum.com/article.aspx?article=105083.



2007 soft lens use by type (US and worldwide)

United States Worldwide

Conventional/PR 19 21

Daily disposable 10 33

Silicone/hydrogel 33 19

HEMA-toric 12 13

Sil/Hyd toric 10 5

Cosmetic tinted 7 6

Multifocal 6 3

Numbers are percent of total soft lens market. PR: planned replacement. Data from: Morgan PB, Woods

CA, Knajian R, et al. International contact lens prescribing in 2007. Contact lens spectrum 2008; 23:36.



FDA classification of soft contact lenses

Group 1

Low water content (<50 percent)

Non-ionic polymer

HEMA hydrogels

Silicone hydrogels

Group 2

High water content (>50 percent)

Non-ionic polymer

HEMA hydrogels only

Group 3

Low water content (<50 percent)

Non-ionic polymer

HEMA hydrogels

Silicone hydrogels

Group 4

High water content (>50 percent)

Non-ionic polymer

HEMA hydrogels only

Reproduced from: US Food and Drug Administration, www.fda.gov/cdrh/contactlenses/lenslist.html.



Silicone hydrogel properties

Proprietaryname

Manufacturer Material Dk Dk/t ModulusWater

content

FDAapproved

wear

FDAgroup

PureVision Bausch andLomb

BalafilconA

91 101 1.10 36 Up to 30days CW

3

Air Optix Nightand Day

CibaVision LotrafilconA

140 175 1.40 24 Up to 30days CW

1

Air Optix CibaVision LotrafilconB

110 138 1.00 38 Up to 6days CW

1

AcuvueAdvance

Vistakon GalyfilconA

60 86 0.40 47 DW-2 wkdisposal

1

Acuvue Oasys Vistakon SenfilconA

103 147 0.75 38 Up to 6days CW

1

Biofinity CooperVision ComfilconA

128 160 0.75 48 Up to 6days CW

1

Avaira CooperVision Enfilcon A 100 125 0.50 46 DW-2 wkdisp

1

CW: continuous wear; DW: daily wear.



Contact lens solutions

Multi-purpose solutions for rinsing, storage and disinfection

• Opti-Free Express (Alcon)

• Opti-Free Replenish (Alcon)

• Complete (AMO)

• Aquify (CibaVision)

• Renu (Bausch & Lomb)

• Sauflon (Sauflon)

• RevitaLens (Abott Medical Optics)

• OptiFree Pure Moist (Alcon)

• BioTrue (Bausch and Lomb)

Peroxide systems

AOSept (CIBA Vision) - Three bottle system: Miraflow (concentrated cleaner), SoftWear saline (torinse off the Miraflow) and AOSept (neutralized by a catalytic disc in the storage case).

Clear Care (CIBA Vision) - Similar to AOSept but a one-step system with cleaner incorporated intothe ClearCare solution and neutralized with a catalytic disc in the storage case.

UltraCare (Advanced Medical Optics) - Four parts: cleaner, saline rinse, peroxide solution and aneutralizing tablet (solution changes color to indicate neutralization).

Sauflon One-Step (Sauflon USA) - One-step system with added wetting agent. Neutralization is witha catalytic disc. Available only through eye care professionals.

Solutions/systems for RGP Lenses

Boston Solutions (Bausch & Lomb) - available retail in three forms: Original, Advance and Simplus

OptiFree GP (Alcon) - available online and limited retail

Optimum (Lobob) - available retail, online and through RGP distributors

Menicare (Menicon) - available online and through RGP distributors

RGP: rigid gas permeable.



FDA guidelines for safe use of contact lenses

• Always wash your hands before handling contact lenses to reduce the chance of getting an infection.

• Remove the lenses immediately and consult your eye care professional if your eyes become red,irritated, or your vision changes.

• Always follow the directions of your eye care professional and all labeling instruction for proper useof contact lenses and lens care products.

• Use contact lens products and solutions recommended by your eye care professional.

• Do not use contact lens solutions that have gone beyond the expiration or discard date.

• Rub and rinse your contact lenses as directed by your eye care professional.

• Clean and disinfect your lenses properly following all labeling instructions provided with your lenscare products.

• Do not "top-off" the solutions in your case. Always discard all of the left over contact lens solutionafter each use. Never reuse any lens solution.

• Never use non-sterile water (distilled water, tap water or any homemade saline solution). Exposureof contact lenses to water has been associated with Acanthamoeba keratitis, a corneal infection that isresistant to treatment and cure.

• Do not put your lenses in your mouth to wet them. Saliva is not a sterile solution.

• Clean, rinse and air-dry your lens case each time lenses are removed. You may want to flip over yourlens case while air drying so excess solution may drain out of the case. Contact lens cases can be asource of bacterial growth.

• Replace your contact lens storage case every 3 to 6 months.

• Do not transfer contact lens solutions into smaller travel size containers. This can affect the sterilityof the solution which can lead to an eye infection. Transferring solutions into smaller size containersmay also leave consumers open to accidentally using a solution not intended for the eyes.

Data from: US Food and Drug Administration, www.fda.gov/cdrh/contactlenses/lenslist.html.



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