contact lens materials

A Look at Lubricating Agents in Daily Disposables
BY JASON J. NICHOLS, OD, MPH, PHD,

We've observed tremendous advances in hydrogel polymer composition in the past few years, first with the incorporation of siloxanes into hydrogels and now with moisturizing or lubricating agents incorporated into lens materials. These materials often provide much needed physiological benefits by increasing oxygen permeability, but they've also introduced new challenges (care and cleaning, complications).

Daily Disposables

Most recently, polymer chemistry advances have made their way into the daily disposable arena, with Focus Dailies with AquaRelease (CIBA Vision) and 1-Day Acuvue Moist (Vistakon).

Questions have circled as to the clinical benefit of these new materials, both relative to their predecessors (Focus Dailies and 1-Day Acuvue) and to the differences between the new materials.

Focus Dailies with AquaRelease (AR) is still manufactured from the nelfilcon A polymer, but is formulated with polyvinyl alcohol (PVA), which is released from the lens during wear. The 1-Day Acuvue Moist (AVM) lens is manufactured from the etafilcon A polymer, but is formulated with polyvinyl pyrrolidone (PVP), which is not released from the lens during wear.

Incorporating these components into the polymers makes the lenses potentially more lubricious, wettable and, ultimately, comfortable.

Comparing Materials

Two studies (Veys and Meyler, 2006; Schwartz and Nick, 2006) address the impact of materials on patient-reported symptoms and satisfaction, and on clinical tests. Both studies were crossover clinical trials of one week of daily wear; no comparisons were made between the new materials and their first-generation predecessors. Table 1 summarizes the results in some outcomes similar to both studies, highlighting the lens in each study that provided superior performance.

To my knowledge, one study (Peterson and coworkers, 2006) compared an older and newer material (Focus Dailies vs. Focus Dailies AR), showing better comfort upon AR application. It also compared Focus Dailies with AquaRelease to another daily disposable (ocufilcon B, CooperVision), showing some improved comfort with the AR lens, but no meaningful differences in clinical outcomes such as noninvasive breakup time, conjunctival staining and corneal staining.

Dr. Nichols is assistant professor of optometry and vision science at The Ohio State University College of Optometry.