GPs Obsolete in 2010? No Way Part 2
BY EDWARD S. BENNETT, OD, MSED
Two surveys provided to Diplomates in the Cornea and Contact Lens Section of the American Academy of Optometry and members of the Association of Optometric Contact Lens Educators (AOCLE)in March supported the idea that GP lenses were found preferable to soft lenses in 13 of 16 categories evaluated. Additionally, a survey of members of the Association of Optometric Contact Lens Educators (AOCLE) showed GP lens use was consistent with prior years in schools and colleges of optometry, while the use of GP educational resources and programs/workshops had increased. However, there are several other issues to address that have been presented by individualsnotably Professor Nathan Efronwho are predicting the demise of GP lenses:
Less Initial Comfort. Granted, otherwise, soft lenses would be in trouble. However, studies show that long-term comfort is equal to soft lenses, and the GP dropout rate is lower. In addition, initial comfort has improved due to manufacturing advances, which have resulted in ultra-thin designs, aspheric peripheries and consistent edges. The use of a topical anesthetic at the initial application also has an impact on patient perception of both adaptation and success.
Parity of Vision. Numerous clinical studies have proven the superior optical quality of non-hydrogel materials. Segmented GP designs provide superior optics and improved vision at all distances. This will only improve as newer segmented GP bifocals with intermediate correction are introduced. Soft bifocals frequently rely on the "20/Happy" principle for patient success. In keratoconus, post-surgical and ocular trauma, GP lenses improve vision significantly. Due to superior optics and greater stability, high astigmatism GP lenses provide better quality vision.
Parity in Ocular Health. Limbal compression, inflammatory reactions, greater binding to lens surfaces and potential for ocular infection result in greater incidence of sight-threatening complications (Keech et al, Optom Vis Sci 1996) for soft lenses. GP lenses approved for extended wear meet the Holden-Mertz criteria for an edema-free state of the cornea with overnight wear, while traditional hydrogels provide only one third of the oxygen required.
No Impact on Myopia Progression in Young People. Several studies, including the Houston Myopia Study (1990) and Yew et al (1999), have found that spectacle-wearing young people increase in myopia from two to three times as compared to GP wearers. The results from the Contact Lenses and Myopia Progression (CLAMP) study from The Ohio State University were not available when this article went to press and should provide the definitive answer to this question.
Orthokeratology/Corneal Reshaping Not Popular. Corneal reshaping has already become popular. The efforts by Paragon Vision Sciences combined with their CRT training/certification sessions and new lens designs have increased the number of practitioners fitting these lenses to well over 1,000. The schools and colleges of optometry have embraced corneal reshaping within their clinical curriculum. Beta research reported by Paragon has shown parents are interested in corneal reshaping for their children. Over 400 practitioners attended the inaugural Global Orthokeratology Symposium in Toronto last August, and a similar number is expected this year.
GP Lenses Fit for Selfish Interests. Some say we fit GP lenses purely to prevent patients from obtaining replacement lenses from alternative distributors. Contact lenses are healthcare devices, not commodities, and patients must perceive them as such. Patients fit with GP lenses avoid alternate distributors, which allow the prescribing practitioner more control over the quality of the fit while ensuring eye health. Fitting spherical GPs in addition to specialty lenses increases patient loyalty, profitability and allows for better patient care.
Dr. Bennett is an associate professor of optometry at the University of Missouri-St. Louis and executive director of the RGP Lens Institute.