Article Date: 4/1/2005

Material Evidence
The latest data reveal which lenses and solutions — and combinations thereof — will help keep your patients in contact lenses. Are you up-to-date?
By Norman Leach, OD, MS, FAAO

How do we prevent contact lens patients from dropping out? Certainly, we need to pay attention to the lens materials we're selecting. But no less important are the solutions we're prescribing and how they interact with different lens materials. And, of course, we need to recognize that patients respond differently on an individual basis to all of these combinations.

Let's review some important information that will help you manage the complexity of your patients' needs.

FDA Groupings

First, we must make sure a contact lens wearer has healthy eyes by confirming a normal tear film and ruling out lid disease, allergy and any other underlying conditions. Then we can logically select lens materials.

As you know, the FDA has established the following categories for contact lenses:

Group 1. Low water (<50%), nonionic

Group 2. High water (>50%), nonionic

Group 3. Low water (<50%), ionic

Group 4. High water (>50%), ionic.

If you select a material based on these FDA groups, patient history, your examination findings and your patients' responses to their existing lenses and solutions, you'll have your best chance of keeping them in contact lenses. However, if the result is less than satisfactory and you feel a change is in order, remember to switch the patient to a different lens material group, not just a different brand within the same group.

Researchers at the University of Waterloo found no significant differences between Night & Day, Acuvue 2, Proclear and Dailies when they were worn by symptomatic and asymptomatic patients for 7 hours.1

Your primary goal should be to maximize comfort. When striving toward that goal, consider two important issues: The effects of deposition and dehydration.

Controlling Deposits

Hydrogel lenses, particularly the high-water types, collect protein deposits. The use of disposables has decreased this problem significantly, but it's still a factor. Mucin and lipid deposits are a little less problematic, but a concern nonetheless. Protein is not such a problem with silicone hydrogel lenses, but lipids may be an issue. Lipid deposits are much easier to control than protein deposits, so silicone hydrogel lenses may be best in terms of spoilage associated with deposits.

Silicone hydrogels also offer the advantage of maximum oxygen permeability. Night & Day (24% water, nonionic, Dk/t 175) and Acuvue Advance (47% water, nonionic, Dk/t 60) are available, and PureVision (36% water, ionic, Dk/t 110) will return to the United States soon. The newest lens in this category is the O2Optix (33% water, nonionic, Dk/t 138). Lens parameters for silicone hydrogels continue to expand, and more lenses, including torics, are on the horizon.

Discomforting Facts

Nearly one-half of the contact lens dropouts identified in a survey of 1,500 spectacle wearers said discomfort was the primary reason they stopped wearing contact lenses. Discomfort was reported three times more frequently than any other reason for dropping out. The survey, conducted in 2004 by CIBA Vision, looked at 1,500 patients between the ages of 12 and 59 and found that 19% were contact lens dropouts.

A total of 1,444 questionnaires completed at 16 eyecare practices found that 34% of patients stopped wearing contact lenses at least once because of discomfort, dryness and red eyes. When asked what it would take for them to resume lens wear, the respondents said improved comfort and relief from dryness. This survey, representing a 33% response, was conducted by researchers at the University of Waterloo.

Dehydration a Factor

All hydrogel lenses dehydrate at a rate of about 7%, although the rate for silicone hydrogels may be 2% or less. Even within an FDA group, the amount and rate of dehydration will differ among materials. However, studies have shown variable correlations between dehydration and patient symptoms. So we have no fixed guidelines to help us choose the most comfortable lens based on dehydration.

Within Group 2 hydrogels, two lenses are reported to be less likely to dehydrate: Proclear (62% water, nonionic, Dk 34) and Extreme H2O (59% water, nonionic, Dk 21). Other lenses on the market may benefit your patients, but remember to consider individual response. For example, I've switched a patient from Acuvue lenses to Proclear lenses to eliminate dryness only to have the patient ask to be put back in the Acuvue. Morgan and colleagues2 compared Proclear and Acuvue during 200-minute sessions in arid, temperate and arctic conditions and found they provided equal comfort.

Find the Right Solution

Another major factor to consider is how compatible your patients' hydrogels and silicone hydrogels are with the solutions they're using. Researchers have conducted several studies of various solutions and lenses, and some have shown complaints of discomfort presumed to be associated with preservatives and/or surfactants.

In one study, 20 of 39 patients using ReNu Multi-Plus Solution experienced increasing discomfort, while fewer than five of 39 patients using preservative-free AOSept Clear Care reported the same problem. The study found that 36% of the patients using ReNu reported end-of-day dryness, while only 12% of the Clear Care users reported the same symptom.

However, not all multipurpose solution products are the same. In clinical studies, Opti-Free Express outperformed ReNu MultiPlus and Complete for end-of day comfort. When measuring frequency of discomfort during the day, the study found that 18% of multipurpose solution users reported complaints, compared to 5% of Clear Care users. These percentages represent patients with complaints every day or most days.

Patients also can develop inflammatory reactions to some polyhexamethylene biguanide (PHMB) solutions. You may be familiar with a report of silicone hydrogel interactions with multipurpose solutions, resulting in extensive staining.3 What's interesting is that most of these patients were fairly asymptomatic.

When choosing solutions for your patients, keep all of these factors in mind. The ideal solution should provide a strong defense against a wide range of microorganisms. It should be compatible with the ocular tissues and with currently available lens polymers, including silicone hydrogel lenses. The solution should also be easy to use and economical for the patient.

Get on Course

I believe we should lean toward silicone hydrogel lenses or the Group 2 lenses. If a patient is experiencing discomfort, prescribe a different multipurpose solution, perhaps one that has a different preservative or hydrogen peroxide, either with his current lenses or a fresh pair of lenses. If this intervention resolves his discomfort, then you'll know the solution has been causing the problem. Switching your patient to one of the solutions, which include enhanced wetting systems, also may make your patient's lens wear more comfortable.

Dr. Leach is a clinical professor of optometry at the University of Houston College of Optometry. He also is director of the Cornea and Contact Lens Service, director of the Cornea and Contact Lens Residency Program and associate director of the Texas Eye Research and Technology Center.

References

1. Fonn D, Dumbleton K. Dryness and discomfort with silicone hydrogel contact lenses. Eye & Contact Lens. 2003;29:101-104.

2. Morgan PB, Efron N, Morgan SL, Little SA. Hydrogel contact lens dehydration in controlled environmental conditions. Eye & Contact Lens. 2004;30:99-102.

3. Lebow KA, Schachet JL. Evaluation of corneal staining and patient preference with the use of three multi-purpose solutions and two brands of soft lenses. Eye & Contact Lens. 2003:29:213-20.

 



Contact Lens Spectrum, Issue: April 2005