EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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38 EW FEATURE February 2011 Refractive challenges and innovations August 2012 Addressing the post-RK hyperopic shift by Michelle Dalton EyeWorld Contributing Writer AT A GLANCE • RK continues to flatten the cornea as patients age—resulting in hyperopic shifts • Post-RK eyes may experience diurnal fluctuations of up to 2 D throughout the day • Crosslinking may be able to alleviate diurnal fluctuations but has not yet been evaluated for its ability to halt the hyperopic shifting • If treating the shift with a lens- based solution, aim for –1 or so, as it may take patients years before they'll progress back to emmetropia Surgical options remain limited, and none can reverse the continued hyperopic progression. But newer techniques may be able to offset the diurnal fluctuations V ery few uncomplicated re- fractive surgeries result in unhappy patients—unless the patient has undergone radial keratotomy (RK). In the post-RK eye, a high percentage (upward of 40%) has hyperopic shifts. Managing continued from page 37 ing the AK on the graft-host inter- face and on the host tissue. "My personal preference is per- forming AK within the graft because I find the graft tissue more reliable as far as the refractive outcome," Dr. Kanellopoulos said. Post-keratoplasty patients require careful monitoring for their refractive stability and the longevity of the graft, Dr. Kanellopoulos said. This includes discussing with patients the possibility of future enhancements. "The goal here is to achieve not necessarily emmetropia but to reduce anisometropia and re- duce significant cylinder to be able to at least bring these patients to a comfortable solution with soft con- tact lenses or spectacles in order to better function in their everyday lives," he said. Future possibilities Greater use of the excimer laser for refractive surgery in post-kerato- plasty patients intrigues a number of surgeons. "Topography-guided abla- tions have the potential to revolu- tionize treatment of all irregular astigmatism, including from PKs. Better ablation profiles and faster treatment times have made me more comfortable with excimer ablations over PKs," Dr. Berdahl said. The use of the laser for more reproducible incisions helps treat astigmatism, but the challenge is how to afford the technology when there is not reimbursement for it, Dr. Lindstrom said. Use of the excimer laser may help revive the older technique of wedge resection, Dr. Kanellopoulos said. "This was performed in the flat meridian of the very significant astigmatism. It has variable results when done by hand and a diamond blade," he said. "Femtosecond and OCT-assisted wedge resections would be a much more predictable proce- dure." Further evolution of phakic IOLs and greater availability of toric pha- kic IOLs would also aid in post-ker- atoplasty refractive surgery, Dr. Kanellopoulos said. Corneal crosslinking may also help in the future to stabilize unsta- ble corneas before refractive treatment, Dr. Berdahl said. EW Editors' note: Dr. Kanellopoulos has financial interests with Alcon. Dr. Lindstrom has financial interests with Abbott Medical Optics (Santa Ana, Calif.), Alcon, Bausch + Lomb (Rochester, N.Y.), and other ophthalmic companies. Dr. Berdahl has no financial interests related to this article. Contact information Berdahl: 605-328-3937, johnberdahl@gmail.com Kanellopoulos: 917-770-0586, ajkmd@mac.com Lindstrom: 952-567-6051, rllindstrom@mneye.com "The most difficult cases to manage are patients with previous RK and progressive hyperopia," said Eric D. Donnenfeld, M.D., clinical professor of ophthalmology, NYU Medical School, New York. "It's ex- tremely common with RK and [has] a direct association with the number of incisions the patient underwent." RK is a procedure that gained popularity in the early 1990s; sur- geons would make radial incisions (typically four or eight incisions per eye) that resulted in a flattened cornea. Retreatments with RK for highly myopic patients resulted in some corneas receiving up to 32 incisions. Unfortunately, it wasn't until the mid-1990s that published studies alerted surgeons to the long- term issues with RK, said Parag A. Majmudar, M.D., associate professor of ophthalmology, Rush University Medical Center, Chicago, and in private practice, Chicago Cornea Consultants Ltd. "RK never stops," he said. "The incisions continue to flatten the cornea and that's what causes the hyperopic shift, and it's progressive. These patients are miserable most of the time." John A. Vukich, M.D., partner, Davis Duehr Dean Center for Refractive Surgery, Madison, Wis., started performing RK in the early 1990s but had abandoned it by 1995. "Many of the RK patients who were in their early 30s at the time of A post-RK compromised cornea Source: Mark Packer, M.D. surgery are now in their 50s. Most of them became presbyopic earlier be- cause of latent hyperopia post-RK. Almost every one of them is back in spectacles and few are happy with their current vision," he said. "Un- fortunately, these were patients we thought we were helping at the time." Complicating matters further for physicians and patients alike is that patients can have diurnal fluc- tuations up to "a couple of diopters of difference," Dr. Donnenfeld said. He added many of these corneas are incredibly flat and cited Ks as low as the mid-30s in some cases. Ideally, he said, the goal is to make these patients emmetropic in the morning and myopic in the evening rather than having them plano in the evening but hyperopic in the morning. "Hyperopia of RK is the gift that keeps on giving," Dr. Donnenfeld joked. Providing better vision The biomechanical stability of the cornea has been lost in a post-RK eye, Dr. Majmudar said. "I tell pa-