EyeWorld Asia-Pacific September 2013 Issue

September 2013 24 EWAP FEAturE Cataract surgery on a post-RK eye Slitlamp view of post-RK eye Uday Devgan, MD Calculating IOL power in post-RK eyes by Michelle Dalton EyeWorld Contributing Writer Some aspects of calcu- lating IOL power in these eyes are easier than it may seem, experts say I n the mid 1980s and early 1990s, radial keratotomy (RK) was a popular means to reduce or eliminate the need for spectacles, but it was gradually phased out in favor of LASIK and PRK. The number of incisions can range from four to 32 in post-RK patients, creating a challenge when these same patients present for cataract surgery. The good news? “It’s actually easier to measure corneal power in the post-RK patient than in the post-laser vision correction patient if you use standard devices,” said Samuel Masket, MD , in private practice, Advanced Vision Care, Los Angeles, Calif., USA, and clinical professor, University of California, Los Angeles. That’s because in the RK eye, both the anterior and posterior surfaces changed in unison, “so reading these with standard instruments gets us much closer to the true value of the cornea.” Although no instrument can read the very center cornea, extrapolating data from all the other curvatures “gets us pretty close.” Dr. Masket firmly believes the post-RK eye “is such a moving target, a multifocal lens should not be considered—it will fail unless we achieve absolute or near emmetropia.” He noted that the refraction can change from morning until evening and there may be progressive hyperopic shift over time. Barbara Bowers, MD , in private practice, Innovative Ophthalmology, Paducah, Ky., USA, disagrees—she’ll bring these patients in at several different times throughout a day “and if the vision is fluctuating a little bit, I’ll consider a multifocal. If they’re fluctuating drastically between the morning and afternoon readings, I’ll tell them point-blank a multifocal lens will make them miserable.” Dr. Masket uses four or five devices to find the flattest Ks, and those are the readings he’ll use for IOL calculation. Astigmatism is an essential component to evaluate in these eyes, said Barry Schechter, MD , in practice, Florida Eye Microsurgical Institute, Boynton Beach, Fla., USA. “We’ve had some very nice results with toric IOLs in RK patients who have varying amounts of regular astigmatism,” he said. “You want to look for wound gaping. If the wounds have healed nice and tight, you’re more likely to get a very stable postop refraction after time, but if you see some gaping, you’ve got the potential for refractive surprises.” If there’s “very irregular astigmatism,” Dr. Schechter advises against a toric—“you just have to go with a plain monofocal aspheric lens. I’ve been surprised with the results obtained and with the range of vision possible due to the spherical equivalent.” Dr. Masket avoids toric lenses in some post-RK patients “for fear AT A GLANCE • Measuring corneal power in the post-RK patient is easier with standard devices. • Multifocal lenses can be an option, but only if vision fluctuation is minimal throughout the day. • Post-RK eyes with irregular astigmatism do better with monofocal lenses. • The more RK incisions, the longer the post-cataract time to refractive stability.