Article Date: 3/1/2010



Get Comfortable With GP Lenses

By Edward S. Bennett, OD, MSEd, FAAO
St. Louis, Mo.

About 10% of contact lens wearers in the United States wear gas permeable (GP) lenses, so it's important to get into a comfort zone with the evaluation and fitting of GP lenses. Here are seven guidelines to help you through the process.

1) Perception. Never use terms such as "uncomfortable" or "discomfort." Tell patients they may experience temporary awareness due to the movement of the lens on the eye and the resulting interaction of the upper lid and the lens edge. Even saying "GP lenses" instead of "rigid" can reduce patient apprehension.

2) Topical Anesthetic Use. The use of a topical anesthetic immediately prior to the initial application of a GP lens is beneficial because it's the initial awareness patients are most concerned about. The anesthetic effect should be allowed to dissipate so the patient will gradually experience GP awareness.

3) Good Initial Vision. Whenever possible, the first pair of lenses the patient wears should be his correct prescription, so he can experience one of the primary benefits of GP lenses — good initial vision. This can be accomplished by empirical design or via fitting from an inventory. Advancements in manufacturing have resulted in consistent, high-quality designs, so GP lenses are almost as easy to work with as soft lenses.

4) Lens Design. The use of larger diameter lenses (9.6 – 11.2mm) reduces lens movement and lid-lens interaction; therefore, initial comfort is often improved. In addition, the use of an ultrathin design in all cases of >1.50D of corneal astigmatism will greatly reduce mass and reduce the likelihood of inferior decentration and corneal desiccation. Ordering all high (> −5D) minus powers with a plus lenticular to minimize edge thickness and a minus lenticular for all plus and low (< 1.50D) minus powers to increase edge thickness may optimize centration and initial comfort.

5) Fitting Relationship. A tucked-under-the-upper-lid fitting relationship is desirable and obtainable for most patients. If the patient has a high (above upper limbus) lid-to-cornea relationship, it's preferable to use a smaller diameter because a lid attachment relationship isn't possible with these patients.

6) Laboratory as a Resource. Your CLMA laboratory can provide you with fitting sets, warranties, and most importantly, consultation on any GP patient or potential wearer.

7) Other GP Resources. The GP Lens Institute ( is the educational division of the CLMA. Its purpose is to develop educational programs and resources for students and practitioners. Resources include an online case grand rounds book pertaining to spherical and special GP lens designs, a lens design laboratory database, GP care and handling brochures and videos, a complete GP presbyopic module and slide set on fitting and troubleshooting, a GP lens management guide and monthly online symposia and webinars. Coming soon, look for a narrated keratoconus management module and the "Click N' Fit" interactive design and fitting program.

Astigmatic, keratoconic, post-surgical and presbyopic patients, as well as soft lens wearers with reduced vision, often achieve the greatest success with GP lenses. Don't be intimidated. In time, you can learn to be a successful GP lens practitioner. nOD

Dr. Bennett is director of student services for the University of Missouri-St. Louis College of Optometry. E-mail him at

Optometric Management, Issue: March 2010