Murat V. Kalayoglu, M.D., Ph.D.
Contributing Editor
Few Ophthalmologists are aware of the history and evolution of a 40+ year refractive treatment called orthokeratology. The practice involves placing a contact lens overnight to reshape the corneal surface in patients with 4-6 diopters of myopia, with or without astigmatism. The individual then removes the lens in the morning, and is able to function throughout the day with >20/40 visual acuity. Importantly, the individual must wear the lenses every night, and sometimes every other night, to maintain uncorrected daytime visual acuity of >20/40. Lenses have advanced to the point where the FDA recently approved several types specifically designed for orthokeratology.
The FDA approval certainly helped bring orthokeratology out from its checkered history marred with complications, and into the center of a heated debate between Optometrists and Ophthalmologists. And given the enormous size of the corneal refractive market and the many alternatives patients have to address their myopia, the debate is sure to rage on for some time.
The first and foremost question is, “is orthokeratology safe”? The FDA approval of the lenses was an important nod to orthokeratology’s safety. For the oprifocon A lens, the FDA approval was based on a multi-center study at 9 investigational sites, conducted on 191 patients (378 eyes) over 9 months. Chief inclusion criteria were myopia between -1.00 and -4.00 diopters, with astigmatism of less than -1.5 diopters. Of the 210 core eyes targeted for emmetropia, 73% had daytime uncorrected visual acuity of 20/20 at 9 months. 95% of these eyes had daytime uncorrected visual acuity of 20/40 or better at 9 months.
Several complications were reported, including bilateral iritis (2 eyes), corneal infiltrates (1 eye), and corneal abrasion (2 eyes). Several patients reported an unexplained decrease in vision. All adverse events eventually resolved without severe complications. Reported symptoms included flaring / ghosting (9%), excessive awareness and pain (2%), red eye or excessive discharge (1%), and photophobia or burning/itching (<1%). The total combined significant adverse effects were 3% in this study.
The FDA approval of the paflufocon lenses was based on a multi-center study at 11 centers, conducted on 122 subjects (240 eyes) over a 9 month period. The study included individuals with myopia ranging from -1.00 D to -6.00 D, with refractive astigmatism of up to -1.75 D. 47% of patients had daytime uncorrected visual acuity of 20/20 or better, and 87% of patients had daytime visual acuity of 20/40 or better. No serious adverse events were reported, although one patient did develop diffuse subepithelial infiltrative keratitis that eventually resolved. 83 subjects discontinued the study, 44 of whom indicated that the treatment led to unacceptable vision.
The chief advantage of orthokeratology is that it allows patients with moderate myopia to avoid surgery for obtaining good uncorrected visual acuity during the day. The anterior cornea undergoes a flattening and temporarily restores uncorrected visual acuity to near-emmetropia levels. Today’s orthokeratology lens material allows excellent transmission of oxygen to the cornea, greatly reducing the chance of corneal ulcers and other complications.
The disadvantage of orthokeratology is that it is temporary; the patient is required to wear a “retainer lens” every night (or sometimes less frequently) in order to maintain the appropriate corneal curvature. Many patients find this difficult to do; indeed, studies submitted to the FDA for approval documented a high (>30%) drop-out rate with many patients finding the treatment too cumbersome, difficult or uncomfortable to continue indefinitely.
In addition, patients may not notice the initial benefits for weeks to months, further reducing compliance. Lastly, the long-term effects of chronic corneal reshaping remain largely unknown. Available data on corneal endothelial integrity suggest that the endothelium is not affected at 1 year; however, will there be a higher incidence of corneal edema in individuals wearing lenses for 3, 5, or even 10 years? Recent data indicate that in addition to anterior corneal flattening, corneas undergoing orthokeratology also have significant posterior flattening, at least during the early adoptive stages of treatment.
Clearly, orthokeratology is not for everyone. However, neither is LASIK. Each patient should choose the right treatment after considering various criteria and alternatives, which are best teased out with the help of their Eye M.D. And maybe, just maybe, the best alternative is to keep wearing those eyeglasses!