Eyeworld

FEB 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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52 EW FEATURE February 2011 Refractive/astigmatism February 2013 Modalities for correcting total corneal astigmatism by Michelle Dalton EyeWorld Contributing Writer With several now available, surgeons weigh in on the pros and cons of each V isually significant astigmatism (generally considered 0.50 D or greater) affects almost 70% of patients presenting for cataract surgery, and most patients expect surgeons to correct the astigmatism along with the cataract surgery. Eric D. Donnenfeld, M.D., partner, Ophthalmic Consultants of Long Island, Rockville Centre, N.Y., and clinical professor of ophthalmology, NYU Medical School, New York, believes that even smaller amounts of astigmatism���perhaps even less than 0.5 D���can be signifi- AT A GLANCE ��� 70% of patients presenting with cataract also have visually significant astigmatism. ��� LRIs can produce exquisite results, but surgeons need to execute them with incredible precision. ��� The variable outcomes with incisional keratotomy may be unacceptable. ��� Femtosecond lasers can create arcuate incisions so precise SIA is minimized. ��� Toric IOLs remain the ���go-to��� choice for higher levels of astigmatism. When performing LRIs, the main points are careful positioning, careful measurements, and careful placement Source: Louis D. Nichamin, M.D. cant. Surgeons need to manage and treat not only pre-op astigmatism, but surgically induced astigmatism (SIA) as well, he said. ���The most common mistake that I see doctors make on a routine basis in treating astigmatism is treating the pre-op astigmatism and not treating the SIA,��� Dr. Donnenfeld said, but noted there are two websites in particular that can help surgeons determine what IOL to use and what the SIA is [www.acrysoftoric.com (Alcon, Fort Worth, Texas) for the former and www.lricalculator.com (Abbott Medical Optics, AMO, Santa Ana, Calif.) for the latter]. For Louis D. ���Skip��� Nichamin, M.D., in private practice, Laurel Eye Clinic, Brookville, Pa., limbal relaxing incisions (LRIs) ���work quite well if you treat them with respect and pay regard to the surgical technique and instrumentation used.��� If surgeons measure the patients��� astigmatism carefully, plan an equally careful surgery, and execute the LRI with a ���great deal of precision, the results can be fabulous,��� Dr. Nichamin said. Although there are ���definitely studies out there indicating better results with a toric lens than with an LRI,��� using a premier diamond blade and paying exquisite attention to the execution levels the field with regard to outcomes, he said. try will become the standard of care in the future enabling practitioners to better achieve the target of emmetropia without astigmatism and possibly other higher aberrations such as spherical aberration and coma. Ultimately this will enable practitioners to put patients within 1/8 of a diopter of spheroequivalent target, the limit of IOLs available in 0.50 D increments, without any residual astigmatism or higher-order aberrations. ���When we do that we���ll have a large number of patients, more than 70%, that are much better than 20/20 because the studies show that approximately 90% of the cataract age group has the neurologi- cal and retinal function that is as good as the vision as when they were 19 years old,��� he said. EW Incisional techniques Advantages of incisional keratotomy over other methods of correcting corneal astigmatism are its lower cost and ease to perform, said Richard Tipperman, M.D., attending surgeon, Wills Eye Institute, Philadelphia. ���But what you���re really Getting continued from page 51 trusting your own experience. He pointed out that while manual keratotomy remains the gold standard, accuracy somewhat depends on operator experience. However, with automated keratometry, there���s often greater ability to duplicate results. For looking at the direction of the astigmatism, however, topography tends to be best. ���If there is a lot of disagreement typically what I���ll do is use automated or manual keratometry to determine magnitude and then use the topography to look at the direction of the cylinder,��� he said. Going forward, Dr. Holladay believes that intraoperative aberrome- Editors��� note: Dr. Holladay has financial interests with Alcon, AMO, WaveTec, and Oculus. Dr. Lane has financial interests with Alcon and WaveTec. Dr. Trattler has financial interests with AMO and Oculus. Contact information Holladay: 713-669-8977, holladay@docholladay.com Lane: 651-275-3000, sslane@associatedeyecare.com Trattler: 305-598-2020, wtrattler@gmail.com after are predictability, reproducibility, and stability,��� he said. ���If you have access to a femtosecond laser for cataract surgery, there���s no question that the incisions are more accurate and more pristine than a blade-created incision,��� he said. Dr. Tipperman also described Richard Mackool, M.D.���s penetrating LRI nomogram, ���where surgeons take their keratome of choice (2.22.5) and make one or two phaco incisions directly on axis to reduce the corneal astigmatism.��� These PLRIs are used just before the viscoelastic is removed at the end of the case, he said. The nomogram shows that for 1.5 D of against-the-rule (ATR) astigmatism, surgeons should make two 3.2-mm incisions 180 degrees apart. ���If you average 100 patients, you���ll have the 1.5 D of correction. But some will have zero effect and others will have a 2.5 D effect,��� Dr. Tipperman said. ���And that���s the issue with incisional keratotomy��� you may on average get your desired effect, but there���s going to be variability that���s hard to control.��� Dr. Donnenfeld uses every technique available but finds he uses diamond knives ���more at the slit lamp to adjust the results in patients who have surprises post-operatively.��� Dr. Tipperman recommends surgeons keep the blades perpendicular to the limbus and ���go slow.��� Study the patient���s topography ���and make sure it���s symmetric and looks good before treating,��� he said. ���It���s amazing the number of people who want to treat based on keratometry readings alone.��� continued on page 54

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