the contact lens exam

Equip Yourself for Modifying GP Lenses

the contact lens exam
Equip Yourself for Modifying GP Lenses


One sign of a successful contact lens practice is the ability to prescribe the best contact lens for any given patient and to then quickly troubleshoot (when necessary) to enhance patient satisfaction. The ability to modify GP lenses in-office offers the benefits of solving problems such as edge-induced lens awareness and variable blurred vision resulting from surface deposits and scratches or adherence, as well as providing a service that is convenient to the patient. The latter benefit is especially important when you consider that patients desire to stay in lens wear without interruption.

Figure 1. Contact Lens Edge Profile Analyzer.

Helpful Hints

Many guidelines can assist you when you want to modify GPs. These include:

► Don't perceive modifying GP lenses as complicated. Almost every procedure individually takes no more than a few minutes and often takes less than one minute.

► Resources are available that can help you, including your Contact Lens Manufacturers Association laboratory consultant (most labs distribute equipment as well), texts such as The Manual of Gas Permeable Contact Lenses from Elsevier and a modification and verification videotape from the GP Lens Institute (

► Modification equipment is relatively inexpensive. To obtain all of the necessary equipment including a bowl, sponges, a spinner and ancillary tools typically costs no more than a few hundred dollars. Equipment is available from Conforma Contact lenses (; G.P. Specialists (; Larsen Equipment Design (; Polychem (; Lamba Polytech (; Valley Contax (; DMV Corporation (; and Key Distributed Products International (888-393-5374). Polish is available from (at minimum) Polymer Tech-nology Corporation ( and Polychem.

► Even if the only modification procedures that you perform in-office pertain to polishing procedures (edge and surface), doing so will manage many of the problems that can occur with GP lenses. Certainly the manufacturing quality of GP lenses continues to improve, resulting in less likelihood that you would find a defective edge; however, if a defect does occur, a simple, easy-to-perform edge polish should eliminate any possible awareness symptoms that a patient would experience.

Various devices are available for edge inspection, but for a "rough" evaluation, simply push the posterior surface across your palm. If it moves freely, then the edge is probably smooth. A nice device for edge profile inspection when used in conjunction with the optics of a radiuscope is the Contact Lens Edge Profile Analyzer (Valley Contax, Figure 1).

►You should be able to modify almost any GP material, although you need to be more careful with high-Dk materials. Using less pressure, a slower spindle speed (if possible) and constant application of polish optimizes success with these materials.

Get Equipped and Get Going

The ability to modify GP lenses is a valuable asset. The rewards are many for practitioners who perform these procedures.

Dr. DeKinder is currently completing a Cornea and Contact Lens residency at the University of Missouri-St. Louis College of Optometry. Dr. Bennett is an associate professor of optometry at the University of Missouri-St. Louis and is executive director of the GP Lens Institute.