EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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August 2012 Refractive challenges and innovations February 2011 EW FEATURE 45 • Try to quantify the treatable regular astigmatism in the central 3 mm zone, paying particular attention to the central flattest and steepest Ks. • Know your SIA and account for it. • Optimize IOL selection and orien- tation by marking patients pre-op- eratively in a seated position and utilizing the real-time refractive data provided by ORA. • Identify refractive surprises and their source quickly and develop a plan. Don't forget to let the patient know. • Be sure to distinguish toric IOL power issues from problems stemming from orientation of the toric IOL. • Consider IOL exchange early when it's easiest and least prone to complication. • Don't be afraid to tell a patient aiming for 20/10 that the "enemy of good is perfect" and that the safest thing to do is nothing. Dr. Berdahl: • Carefully check for dryness and ABMD pre- and post-operatively. • If ABMD is present, do PRK instead of LASIK. • Understand when to rotate the IOL, exchange the IOL, or perform excimer photoablation. • The most accurate way to rotate the IOL to the new position is to use the current location as a refer- ence point and rotate the IOL the proper amount from the reference point, i.e., in this case rotate it 24 degrees counterclockwise from the current location, as opposed to marking the cornea at 170 degrees and rotating it to that position. This mitigates cyclotorsion errors. Dr. Solomon: In this case, the corneal surface does not reveal any evidence of basement membrane changes, degenerative changes/nod- ules, or evidence of any pathology. While the astigmatism is asymmet- ric, it is not irregular and lines up repeatedly along a distinct axis. It is not unusual to find different devices measure the corneal curve with dif- ferent techniques and slightly differ- ent areas of the cornea. In this case, this patient was satisfied with his previous vision prior to the develop- ment of cataracts with glasses. He is not a contact lens wearer (and his vision did not improve pre-op with a hard contact lens over-refraction). Given his pre-op history of good vision with spectacles and his motivation to be less dependent on corrective eyewear for distance, it seems reasonable to consider a toric IOL. In closely looking at his pre-op corneal measurements, his manual keratometry and topography meas- urements (drawing a line through the steep axis) lined up quite well. Hence, 153 degrees was used in the toric calculator. Taking into account the surgically induced astigmatism from the clear corneal incision for his cataract surgery, the toric calculator indicated his toric IOL (T3, Alcon) should be oriented at 144 degrees. Post-operatively, his residual astigmatism (+1.25 diopters) was oriented at 15 degrees. This post-op refraction, while unex- pected, is part of the art and science of refractive cataract surgery. As Dr. Berdahl suggested, the posterior corneal surface, as recently pointed out by Dr. Koch, may play a more integral role in some patients more than others. Options that I considered for this patient are: LASIK or PRK enhancement versus IOL exchange with use of intraoperative aberrome- try (ORA) to fine-tune the refractive outcome versus IOL repositioning. In this case, the website developed by Dr. Berdahl and David Hardten, M.D. (astigmatismfix.com), indi- cated that rotating the current toric IOL 149 degrees clockwise to a final resting position of 175 degrees should leave the patient with a residual refractive error of –0.33 + 0.42 axis 168 and a spherical equiva- lent of –.12 diopters. This was quite acceptable to me. A second surgery was performed and the currently im- planted toric IOL was rotated to the axis of 175 degrees. Intraoperative aberrometry with ORA confirmed minimal residual refractive error. One month post-operatively, the patient had an uncorrected vision of 20/20 with a refraction of –0.25 + 0.25 axis 110. The patient is ex- tremely happy with his result and pleased that I was willing to do whatever it took to fix the problem. Residual uncorrected refractive error is one of the most common reasons for an unhappy patient following refractive surgery or refrac- tive cataract surgery. In my experi- ence, patients are more disappointed if a physician is not receptive to their concerns and not willing to commit to their issues. In this case, the patient's uncorrected vision was 20/40 and BCVA was 20/20 (im- proved from a pre-op BCVA of 20/50). In some ways, one could make the argument that he "should be happy." In being willing to listen to the patient's concerns and under- standing his desire to be less de- pendent on glasses, we took a potentially unhappy patient and converted him to an extremely happy and satisfied patient. In fact, this patient was never afforded the opportunity to become unhappy. I identified with his concerns imme- diately and presented options (in- cluding glasses) for a solution. The patient was not upset that he did not reach his refractive target the first time around, was understand- ing that medicine and science is not perfect, and was grateful for my suggestions and ultimate solution to his problem. EW Editors' note: Dr. Berdahl has financial interests with Alcon, Allergan (Irvine, Calif.), and ISTA Pharmaceuticals (Irvine, Calif.). Dr. Desai has financial interests with Alcon, Allergan, Bausch + Lomb (Rochester, N.Y.), Bio-Tissue (Miami, Fla.), Inspire Pharmaceuticals (Raleigh, N.C.), WaveTec Vision, and TruVision (Santa Barbara, Calif.). Dr. Solomon has financial interests with Abbott Medical Optics (Santa Ana, Calif.) and Alcon. Contact information Berdahl: 605-328-3937, johnberdahl@gmail.com Desai: 727-518-2020, desaivision@hotmail.com Solomon: kerry.solomon@carolinaeyecare.com Poll size: 304 EyeWorld Monthly Pulse EyeWorld Monthly Pulse is a reader survey on trends and patterns for the practicing ophthalmologist. Each month we send a 4-6 question online survey covering different topics so our readers can see how they compare to our survey. If you would like to join the current 1,000+ physicians who take a minute a month to share their views, please send us an email and we will add your name. Email daniela@eyeworld.org and put EW Pulse in the subject line; that's all it takes. Copyright EyeWorld 2012