Article Date: 9/1/2005

discovering dry eye
Dry Eye News From the BCLA
BY JASON J. NICHOLS, OD, MPH, PHD

For those of you unfamiliar with the British Contact Lens Association (BCLA), it's an organization that strives to promote the clinical practice and science of contact lenses. At this year's meeting, there were more than 1,200 participants from more than 40 countries. Following are some highlights of significant research or events related to the tear film, dry eye and contact lenses from this year's meeting.

Studying Tear Mixing

Dr. Ken Polse gave the BCLA Medal address, presenting an account of his research that originally centered on corneal hypoxia related to lens wear and has more recently focused on "tear mixing." The main goal of the tear mixing lab at the University of California is to understand factors that control tear mixing under a contact lens, such as post-lens tear film thickness, lateral and transverse lens motion, material modulus and overall diameter. The lab has also focused on the impact of lens fenestrations relative to improving tear exchange.

Silicone Hydrogel News

Vistakon announced the launch of its Acuvue Oasys (senofilcon A) and 1-Day Acuvue Moist contact lenses. Oasys is a new silicone hydrogel lens that Vistakon is targeting for the contact lens-related dry eye population. It has a Dk/t of 147 and doesn't have a surface treatment, but rather incorporates polyvinyl pyrolidone (PVP), which may improve wettability. The 1-Day Acuvue Moist is a daily disposable lens that is similarly targeted for the contact lens-related dry eye population.

Coopervision announced the development of its new silicone hydrogel material, comfilcon A. While maintaining a significant Dk/t, the material is "naturally wettable" and doesn't have a surface treatment or wetting agents. Further, the material has a lower modulus and higher water content than other available silicone hydrogel materials, which may improve wearing comfort.

Drs. Brian Tighe and Lyndon Jones independently presented scientific research on biocompatibility and wettability of silicone hydrogels. Dr. Tighe's group reported that the new Acuvue PVP-associated materials had lower advancing contact angles when fully hydrated and low coefficients of friction in comparison with the other silicone hydrogels, and that CIBA Vision's Focus Dailies (nelfilcon A) can release polyvinyl alcohol (PVA), which should, in theory, improve lens and tear film interaction.

Dr. Jones's group, based at the University of Waterloo, showed that traditional hydrogel lenses were associated with good initial comfort, but end-of-day discomfort corresponding to decreased wettability. Silicone hydrogel contact angles were initially high, but decreased over the day's wear; various multipurpose solutions as well as protein and lipid deposits can also significantly impact these contact angles.

Surfactant Action

Research from Alcon Laboratories showed that the use of surfactants (particularly tetronic 1304) in multipurpose solutions has a significant impact on hydrogel lens wettability. Surfactants work by reducing the surface tension of a film, allowing for an even and uniform spread of the tear film over a lens.

Strides in Tear Film Analysis

Drs. Kelly Nichols and Franz Grus independently presented new mass spectrometry-based analytical methods for analyzing tear film lipids and proteins, respectively. These methods have significant promise in targeting biomarkers associated with dry eye disease in general, or potentially for the contact lens wearer. Manufacturers may then target these biomarkers relative to specific pharmaceuticals or lens care cleaning products.

A Clear Goal in Mind

As this and other scientific work translates into patient care, it's clear that the contact lens field as a whole is aimed at targeting contact lens-related dry eye.

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

 


Contact Lens Spectrum, Issue: September 2005