discovering dry eye
Consider Silicone Hydrogels for Dry Eye Patients
BY KELLY K. NICHOLS, OD, MPH, PHD
When a new lens enters the market, we want to understand what type of patients will benefit most from switching to it. In other words, we want to know what makes it better, stronger and more comfortable than its competitors. In dry eye disease, particularly contact lens-related dry eye, contact lens practitioners are generally willing to try new lenses and new products with their patients in hopes that they'll find the "magic bullet."
When silicone hydrogels first entered the marketplace, they didn't generate much buzz related to dry eye. After all, these lenses were designed for overnight wear, and patients who can sleep in lenses don't have contact lens-related dry eye. Then practitioners began to recommend them for daily wear on a case-by-case basis, even for dry eye patients. Anecdotal evidence began to surface that dry eye patients thought the lenses were more comfortable than their habitual lenses.
Relieving End-of-Day Dryness
End-of-day dryness is a hallmark symptom of contact lens-related dry eye. Patients often complain that they can't wear their contact lenses comfortably for as many hours as they'd like.
Unpublished data from researchers at The Ohio State University have demonstrated that patients wearing Focus Night & Day lenses (CIBA Vision) had significantly less end-of-day dryness (Schaffer et al 2003). While this study demonstrates an important finding, the researchers weren't trying to determine whether contact lens-related dry eye patients achieved longer, more comfortable wear. If we can determine what type of lens these patients would succeed with, then patients and practitioners (and manufacturers) would be happy indeed.
Vistakon recently launched Acuvue Advance in a new silicone hydrogel lens material. It's a Group 1 lens, but the water content is among the highest in the group. The lens material has an internal wetting agent called Hydraclear that's designed to maintain lens hydration. Vistakon clinical studies have shown that significantly more patients wearing Acuvue Advance can wear their lenses comfortably longer (nine to 18 hours) compared to Acuvue 2 and Night & Day wearers (see Figure).
More Study Required
However, again that study didn't set out to determine which lens patients who have lens-related dry eye would prefer. Such studies are difficult to perform. First, we need a consensus on the entry criteria for contact lens patients who have dry eye. Which tests should researchers select? Tear break-up time? Schirmer test? Fluorescein and lissamine green staining? Second, we need to select a suitable outcome. Which is most important -- increased comfortable wearing time? Lack of lens sensation for a set period of hours? Patient preference?
While researchers struggle with the details, practitioners will continue to try different lenses, including Acuvue Advance, on dry eye patients and patients who experience reduced comfort with other contact lenses. And, for some, it will work.
Dr. Nichols is assistant professor of clinical optometry at The Ohio State University College of Optometry in the area of dry eye research.