EyeWorld India March 2013 Issue

March 2013 12 EWAP FEATURE 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, MD , partner, Ophthalmic Consultants of Long Island, Rockville Centre, NY, USA, and clinical professor of ophthalmology, NYU Medical School, New York, NY, USA, believes that even smaller amounts of astigmatism—perhaps even less than 0.5 D—can be significant. 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, USA/Hünenberg, Switzerland] for the former and www.lricalculator. com [Abbott Medical Optics, AMO, Santa Ana, Calif., USA] for the latter). For Louis D. “Skip” Nichamin, MD , in private practice, Laurel Eye Clinic, Brookville, Pa., USA, 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. Incisional techniques Advantages of incisional keratotomy over other methods of correcting corneal astigmatism are its lower cost and ease to perform, said Richard Tipperman, MD , attending surgeon, Wills Eye Institute, Philadelphia, Pa., USA. “But what you’re really after are predictability, reproducibility, 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. Views from Asia-Pacific Johan A. HUTAURUK, MD Director, Jakarta Eye Center Jl. Cik Ditiro 46, Menteng, Jakarta – 10310 Indonesia Tel. no. +62-21-2922-1000 Fax no. +62-21-390-4601 johan.hutauruk@jakarta-eye-center.com C ataract surgery has now become cataract refractive surgery, because the target is not only visual rehabilitation by removing the cloudy lens but also to optimize the visual acuity postoperatively, so our patients can expect to be free of glasses. Almost 70% of patients presenting with cataract also have astigmatism, this is a huge number but fortunately, most of them have less than 1.0 D of astigmatism. Hoffer reported 23% of eyes exhibited more than 1.5 D of astigmatism in a series of 7500 patients undergoing cataract surgery and others reported that only 8% exhibited >2.0 D of corneal astigmatism and 2.6% exhibited >3.0 D. Peripheral corneal relaxing incisions are still the most cost effective modalities to treat preexisting astigmatism, and the nice thing about this procedure is that we don’t have to be so accurate but results will almost always reduce the astigmatism. For example, most patients with <1.0 D astigmatism can be treated by placing the phacoemulsification on the steep corneal meridian. This is the simplest method to take advantage of SIA (surgically induced astigmatism) to neutralize the preexisting astigmatism. Limbal relaxing incisions (LRI) are the low-cost approach for correction of corneal astigmatism between 1 and 3 D, but I still prefer to opt for toric IOLs for better reliability if the patient can afford premium IOLs. Toric IOLs are easier to adopt since they do not need any additional procedures other than marking the axis and rotating the toric lens at the end of surgery. We are aware that the precision of refractive outcome after cataract surgery is only half compared with LASIK. Only 45% of cataract surgeries are within 0.5 D of targeted refraction with current biometry compared with 90% in LASIK. Patients with high corneal astigmatism of >3 D, which is less than 2.5% of the cataract population, might benefit from LASIK touch up to reduce the corneal astigmatism as well as any residual refractive errors. In my opinion, the best way to correct corneal astigmatism in cataract patients is to correct the cause of astigmatism, which is in the cornea, rather than to compensate it with a toric lens. LRI fits with this idea and femtosecond laser cataract surgery has an added value of creating precise arcuate corneal incisions. Corneal topography should help to detect asymmetric corneal astigmatism and if there is an irregular astigmatism then topography guided LASIK would be the best option. Editors’ note: Dr. Hutauruk has no financial interests related to his comments.