Global GP Fitting
BY EDWARD S. BENNETT, OD, MSED
The third annual Global Orthokeratology Symposium (GOS) in Chicago represented a tribute to the interest in this emerging contact lens specialty. In addition to the educational sessions that highlighted new research and advances in corneal reshaping as well as clinical applications, problem-solving and marketing this modality, GOS offered certification for one or more lens designs including Paragon CRT (Paragon) and the four lens designs associated with Bausch & Lomb's Vision Shaping Treatment: BE Retainer (Precision Technology Services, Ltd., beretainer.com), Contex OK E-System (Contex, www.oklens.com), DreamLens (DreimLens, Inc., www.dreimlens.com) and Emerald (Euclid Systems Corp., www.euclidsys.com). Many attendees took advantage of this opportunity.
News from the Sessions
Highlights of the GOS educational sessions included the following:
An excellent session on myopia. Earl Smith III, OD, PhD, showed how important the peripheral retina is for regulating emmetropization a functioning fovea isn't essential for this purpose. Jennifer Choo, OD, and Pat Caroline, FAAO, showed how corneal reshaping lens designs have great potential to provide a clear focus at the retinal periphery, including a formula that could prove useful in creating future lens designs for this purpose.
Jeff Walline, OD, PhD, provided the final results of the Contact Lenses And Myopia Progression (CLAMP) study, which showed that standard GP contact lenses fit to young people reduced myopia progression (–1.56D increase vs. –2.19D for soft contact lens wearers over three years) but resulted in no difference in axial length. Pauline Cho, BOptom, PhD, however, found with 7- to 12-year-old corneal reshaping patients that changes in the axial length and vitreous chamber depth were both approximately half those of spectacle-wearing controls after a two-year period.
A look at microbial keratitis with ortho-k. Jonathan Jacobson terms this "SORS" (Somber Orthokeratology Reports Syndrome), as some of the documented, heavily publicized reports aren't well researched or balanced. Helen Swarbrick, OD, PhD, and Kathleen Watt reported that 50 cases of microbial keratitis with corneal reshaping occurred from 2001 to 2005, 80 percent of which were from East Asia. Risk factors included inappropriate lens care (exposure to tap water, noncompliance with lens care [saline storage], persisting in lens wear despite symptoms and inappropriate wearing schedule [failure to remove the lenses during the day]). With the relatively low number reported from other global regions, they believe that it's premature to indicate that an increased risk for microbial keratitis exists with corneal reshaping as compared to other contact lens modalities.
New applications of corneal reshaping including hyperopic and presbyopic lens designs that have resulted in a surprisingly high rate of success.
Cary Herzberg, OD, reported that use of a high-viscosity lubricant before application of corneal reshaping lenses results in both better corneal health and improved corneal molding.
According to Michael Lipson, OD, in comparing overnight corneal reshaping to soft disposable lenses in a crossover study, more than two-thirds of the study population preferred to stay in corneal reshaping at the conclusion of the study.
In summary, it's evident that corneal reshaping is beginning to boom. With their ability to reduce axial length in young people complemented by the knowledge we now have about emmetropization, corneal reshaping lenses have the exciting potential to play a significant role in optimizing focus of light on the peripheral retina and impacting myopia progression.
Dr. Bennett is an associate professor of optometry at the University of Missouri-St. Louis and is executive director of the GP Lens Institute.