EyeWorld Asia-Pacific September 2012 Issue

September 2012 10 EWAP FEAturE Addressing the post-RK hyperopic shift by Michelle Dalton EyeWorld Contributing Editor 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 refractive 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. “The most difficult cases to manage are patients with previous RK and progressive hyperopia,” said Eric D. Donnenfeld, MD , partner, Ophthalmic Consultants of Long Island (OCLI), Rockville Centre, NY, USA, and clinical professor of ophthalmology, NYU medical school, New York, NY, USA. “It’s extremely 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; surgeons would make radial incisions (typically four or eight incisions per eye) that resulted in a flattened cornea. Re-treatments 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, MD, associate professor of ophthalmology, Rush University Medical Center, Chicago, Ill., USA, 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, MD, partner, Davis Duehr Dean Center for Refractive Surgery, Madison, Wis., USA, 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 surgery are now in their 50s. Most of them became presbyopic earlier because of latent hyperopia post-RK. Almost every one of them is back in spectacles and few are happy with their current vision,” he said. “Unfortunately, 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 fluctuations 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 patients we can remove the hyperopia today, but in 6 months or a year that might change. If the cornea continues to get more ectatic in the mid-periphery, the hyperopia will return.” Surgeons basically have three options, he said: LASIK, PRK, or (if age appropriate) cataract surgery. Creating a LASIK flap after RK can result in irregular astigmatism because of potential flap issues, so Dr. Majmudar doesn’t recommend it. “RK and LASIK are incompatible,” Dr. Vukich said. “The hyperopic shift is a corneal problem, and placing horizontal transecting incisions into vertical incisions is a recipe for disaster.” When he did perform LASIK on these eyes in the past, Dr. Donnenfeld said some patients had issues with the RK incisions splitting, creating a “pizza pie- like appearance.” If he can obtain wavefront aberrometry, he’s comfortable performing PRK but offered a few pearls. First, he said, if there are epithelial inclusion assists within the incisions themselves, it indicates the incisions are spreading. He prefers to clean out the incisions with a Sinskey hook and suture them closed with non-biodegradable sutures (such as 10-0 prolene). Suturing will hold the incisions together and, by tightening, may result in reversing some of the hyperopia and astigmatism that’s been caused in the area. He also uses mitomycin-C for 30 seconds (0.02 mg/mL) instead of the typical 12 seconds in surface ablation. “I’d rather steepen the cornea AT A GLANCE • Radial keratotomy 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 A post-RK compromised cornea. Source: Mark Packer, MD continued on page 16