EyeWorld India March 2013 Issue

15 March 2013 EWAP FEATURE Experts differ on corneal astigmatism correction in cataract surgery by Erin L. Boyle EyeWorld Senior Staff Writer Total corneal astigmatism correction during cataract surgery could be either by eliminating it or leaving slight with-the-rule astig- matism C orneal astigmatism correction in cataract surgery should achieve zero residual astigmatism, some experts say, but there is also a theory that patients might benefit from one quarter to one half a diopter (D) of with-the-rule astigmatism because of against-the- rule drift. Jack T. Holladay, MD , clinical professor of ophthalmology, Baylor College of Medicine, Houston, Texas, USA, said the goal in corneal astigmatism correction should be to eliminate it completely. “The idea that you should leave a little with-the-rule and against- the-rule are old myths that come from articles written about 10 or 15 years ago,” said Dr. Holladay. “It’s not true. Residual astigmatism is like any other aberration. The best vision and the best result are with zero residual astigmatism and with- or against-the-rule are not beneficial. They blur the image, particularly if you don’t wear glasses.” The ultimate goal in patient management for total corneal astigmatism correction in cataract surgery is both short-term and long-term patient satisfaction, said Douglas D. Koch, MD , professor and the Allen, Mosbacher, and Law Chair in ophthalmology, Cullen Eye Institute, Baylor College of Medicine. He said a key step in achieving that goal is determining patients’ needs. “If we go to the assumption that most patients want to see clearly at some distance without glasses, and therefore have a significant reduction of their astigmatism, the goal in my mind would be a small amount of with- the-rule astigmatism, around 0.25 D or at most 0.5 D, the reason for that being there’s a long-term against-the-rule shift that takes place. If you leave patients with just a little bit of with-the-rule astigmatism, that will enable them to maintain a relatively small amount of astigmatism over a long period of time,” Dr. Koch said. “We should also recognize that occasionally patients do well with myopic astigmatism, which gives them greater depth of focus, but at the expense of clear vision at any distance. It is difficult to predict those who might like this, so I rarely recommend it,” he said. Patient age Dr. Koch has been researching corneal astigmatism and toric IOL selection in cataract surgery cases. He has developed a nomogram that incorporates the mean posterior corneal astigmatism in eyes with either with-the-rule astigmatism or against-the-rule astigmatism and the effect of against-the-rule drift that happens with aging. Warren E. Hill, MD , East Valley Ophthalmology, Mesa, Ariz., USA, said that he follows Dr. Koch’s recommendation of leaving patients with one quarter to one half a D of with-the-rule astigmatism as the final operative goal. “I think that’s a very good strategy. Typically what happens for the older patients is that they may gain a little against-the-rule astigmatism over time, so if you leave them with some with-the- rule astigmatism, they’ll always be changing toward something better [rather] than away from what it is that they want,” said Dr. Hill. AT A GLANCE • Some experts say the goal in total corneal astigmatism correction is eliminating it. • Theory postulates that one quarter to one half D of with- the-rule astigmatism could be effective. • Against-the-rule drift that happens with age could play a role in effectiveness. • With-the-rule astigmatism cases are easier to treat, expert says. Dual Scheimpflug image showing more than 3 D of WTR astigmatism on the anterior cornea and –0.65 on the posterior cornea (which has an ATR refractive effect) Source: Douglas Koch, MD, and Wang Li, MD continued on page 16