EyeWorld India December 2013 Issue

7 December 2013 EWAP FEAturE continued on page 8 Diagnostic tools’ use increasing by Michelle Dalton EyeWorld Contributing Writer The more sophisticated the technology, the better to evaluate patients with astigmatism P atients with preexisting astigmatism need a battery of tests before undergoing cataract surgery—tests that can help surgeons determine what axis the astigmatism is on, the magnitude of the astigmatism, and the amount of irregularity of the astigmatism. A decade ago, manual Ks were commonly used, said Jeffrey D. Horn, MD , in private practice, Vision for Life, Nashville, Tenn., USA. In those days, he’d use the plus sign on the manual keratometer for both axes, but would also include Orbscan (Bausch+Lomb, Rochester, NY, USA) readings and topography “to make sure that there wasn’t any irregularity to the astigmatism.” These days, however, manual Ks alone just don’t cut it. “You cannot effectively, consistently treat preoperative astigmatism with only a manual keratometer, period. The reason is it cannot adequately determine irregular or asymmetric astigmatism,” said Kevin Waltz, MD , in private practice, Eye Surgeons of Indiana. “Our job is to figure out whether the astigmatism is corneal or lenticular or a combo of both of those things. Usually my cataract patients get diagnostic topography to give me an idea of whether or not the manifest refraction matches their keratometric cylinder,” said Sonia Yoo, MD , professor of ophthalmology, Bascom Palmer Eye Institute, Miami, Fla., USA. Keratometers are typically set around 2.6 mm, “so they’re very Topography can help confirm the axis of astigmatism and the quantity of the astigmatism in addition to irregularities, including asym- metry. Source: Christopher Hodge, Vision Eye Institute good for the central cornea, but not very good at the mid-periphery points,” Dr. Waltz said. “You need topography to look at the qualitative aspect of the cylinder.” William Trattler, MD , in private practice, Center for Excellence in Eye Care, Miami, Fla., USA, is a fan of using topography to help confirm the axis of astigmatism and the quantity of the astigmatism in addition to irregularities, including asymmetry. “It also helps determine if there is any dryness; you can see the quality of the tear film just by looking at the maps,” he said. Consistency in numbers is the driving force behind numerous tests patients undergo at Wallace Eye Associates (Alexandria, La., USA), said R. Bruce Wallace III, MD , founder and medical director. He wants to ensure the axis matches properly, the corneal cylinder matches, and if they don’t, “we tell patients they’ll likely need an astigmatic correction, and if the cylinder is low enough, we’ll do the limbal relaxing incision in conjunction with the cataract surgery,” he said. Robert T. Crotty, OD , clinical director, Wallace Eye Surgery, said in general, the group uses autorefractors, corneal topography, K readings from an IOLMaster (Carl Zeiss Meditec, Jena, Germany) “to make sure the dioptric values correlate with each other, and in some cases we’ll even throw in manual keratometry for reassurance.” Manual Ks are not obsolete, however. Dr. Horn still defers to his manual keratometer when there are “significant differences” between the topographer, refraction, Lenstar (Haag-Streit, Koeniz, Switzerland), and Pentacam (Oculus, Wetzlar, Germany) readings, or when those readings “constantly change from visit to visit.” The symmetry of any K reading is equally important, Dr. Trattler said. Variability in corneal AT A GLANCE • Manual Ks are helpful, but topography is necessary to rule out irregularities. • Topography analyzes the qualitative aspects of the cylinder. • Sophisticated technology can help reduce enhancement rates to low single digits.