In Search of . . .
The Perfect Contact Lens

BY CRISTINA M. SCHNIDER, O.D., M.Sc., F.A.A.O.
JAN. 1996

With the beginning of a new year already upon us and the dawn of a new century just around the corner, I find myself wishing for that perfect contact lens and hoping that it will magically appear sometime soon! Even though many of us believe that RGP lenses offer much of what we'd like to see in the lens of the future, there are also some features we'd like to change.

OXYGEN TRANSMISSIBILITY

In designing the ideal lens, my primary goal would be safe, healthy, continuous wear, or extended wear with very infrequent lens removal for cleaning. Therefore, an important characteristic would be very high oxygen transmissibility.

Based upon work by Bonanno and Polse and others, I'd also ensure that carbon dioxide could pass through the lens easily. Oxygen is the stuff of life, at least for humans, and its by-product, CO2, is responsible for many of the physiological changes we see in contact lens wearers. Fortunately, we have nearly achieved these Dk goals.

ADEQUATE TEAR EXCHANGE

The tear exchange characteristics of RGP lenses are beneficial because they clear debris and waste material from beneath the lens. However, most soft contact lenses don't provide adequate lens movement to accomplish good tear exchange. How much movement is enough for adequate tear exchange while not compromising comfort? This is an ongoing challenge for researchers in the high Dk soft lens development area even as we speak. Early research with high Dk soft contact lenses has demonstrated that improving the oxygen transmissibility yields vastly improved physiological response, but it doesn't eliminate the inflammatory problems that plague patients in hydrogel extended wear lenses.

BIOCOMPATIBILITY

Surface characteristics and material flexibility also challenge our researchers. Obviously, to meet the goal of continuous wear, a contact lens material must be supremely biocompatible with the ocular surface and adnexa. Rigid lenses are probably closer to this ideal than soft lenses, but we still must characterize the process of inflammation and immune response, and design a material that blocks or at least does not initiate these processes.

REMEMBER THE OPTICS

While wrestling with these complex issues of cellular biology, we must not forget that optics are part of our job as well! The material flexibility issue is a double-edged sword, much like that of lens movement. We want a lens rigid enough to correct astigmatism, or at least stable enough to permit manufacture of toric and complex designs, but soft enough to provide relatively good comfort.

A BUSINESS PLAN FOR THE FUTURE

The final aspect of designing the lens of the future is the business side of the plan. How affordable should this lens be? How available should it be? Should there be some means of planned obsolescence that will compel patients to return to eyecare practitioners for proper care and lens replacement?

We need to focus on our patients/customers, and give them what they want. I have a simple formula for value:

x (need) + y (cost) + z (convenience) = VALUE

We must give our patients something they need, make it affordable (but not necessarily cheap) and convenient. We should be "selling" our services not our commodities.

With the help of scientists and researchers in many fields, we may soon have this ideal contact lens, but as professionals, we still must find that niche of service that will secure our long-term livelihood. CLS

Dr. Schnider is an associate professor at Pacific University College of Optometry, Forest Grove, Ore. She is on the FDA Ophthalmic Devices Panel.