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EW REFRACTIVE SURGERY 70 March 2016 split-radial incision. It will help close your wound. You should also use sealant." Following cataract surgery, it can take patients who have had RK a longer period of time to become refractively stable. "I usually wait about 5 months to see if the topog- raphy changes," Dr. Yoo said. "If it has not changed, then it would be helpful to consider a piggyback lens." To select the appropriate power of the piggyback lens, Dr. Yoo sug- gested using the Masket nomogram. "For hyperopic refractions, we take 1.5 times the spherical equivalent to determine what power of lens to put in the sulcus," she said, noting for myopic refractions, the nomogram recommends taking 1.2 times the spherical equivalent to arrive at the correct power of lens to place in the sulcus. For patients who have kerato- conus or pellucid marginal degen- eration, a toric lens can be placed if the ectasia is stable and if patients historically have had good best spectacled-corrected visual acuity. Dr. Yoo cited a case of a 51-year- old patient with a history of pene- trating keratoplasty and subsequent cataract surgery with a toric IOL to remedy post-transplant astigmatism. Prior to failure of the graft, the pa- tient had uncorrected visual acuity (UCVA) of 20/40. For such a patient, Descemet's stripping automated en- dothelial keratoplasty was performed and allowed the patient to regain UCVA of 20/50. The experience serves as a clinical pearl for ophthalmologists: For patients who have had corneal grafts, if there is suspicion of a high likelihood of needing to replace the graft within the next decade, it is a judicious move not to use a toric IOL. EW Reference 1. Ianchulev T, et al. Intraoperative refractive biometry for predicting intraocular lens power calculation after prior myopic refractive sur- gery. Ophthalmology. 2014 Jan;121(1):56–60. Editors' note: Dr. Yoo has no financial interests related to this article. Contact information Yoo: syoo@med.miami.edu by Louise Gagnon EyeWorld Contributing Writer techniques outside of conventional methods such as the Shammas for- mula, Haigis-L formula, or surgeon's preoperative choice based on the available clinical data. In a series of 215 patients/246 eyes, investiga- tors found intraoperative refractive biometry (IRB) produced the greatest predictive accuracy with a median absolute error of 0.35 D and mean absolute error of 0.42 D. Specifically, 67% of eyes were within 0.5 D, and 94% were within 1.0 D of the IRB's predicted outcome. 1 The presence of astigmatism in a patient presents a challenge in proper lens positioning. To address this challenge, Dr. Yoo suggested cli- nicians find ways to make sure their incisions are on axis. "Photographic axis marking avoids cyclotorsion error," she said. "If you are putting in a toric lens because the patient has astigmatism, there are different devices that can help align the toric lens. There are intraoperative axis marking devices that can be inte- grated into the microscope." But even with a topography device, clinicians can look at scleral vessels on the eyes, for example, and make markings to use as reference points to ensure the cuts are on axis in the presence of high degrees of astigmatism, Dr. Yoo said. When performing radial kera- totomy (RK) incisions, there is a risk of wound dehiscence. In terms of dehiscence of an RK incision during cataract surgery, wound dehiscence can be avoided through several steps including decreasing infusion pressure, operating between radial incisions, and using a scleral tunnel in lieu of a corneal tunnel, Dr. Yoo said. "When you have an open RK wound, and you have an incision that crosses it in a T pattern, there is a way to suture these closed and a way not to suture these closed," Dr. Yoo said. "As you throw sutures across the wound, it starts to gape or pull open your corneal incision." This surgical approach may increase the risk of the cornea leaking postoperatively and not being sealed. "When you have an open RK wound and a wound across it, it is preferable to use a figure 8 suture," said Dr. Yoo. "It should span your corneal incision and cross the ahead to reach the target goal for their vision. "People who have had prior refractive surgery may need to know it's more difficult to reach a desired refractive outcome," Dr. Yoo said. "You may have to perform multiple procedures to get the best desired end result. Patients who have hyper- opic corneal refractive surgeries tend to end up with myopic refractive surprises, and vice versa." A growing segment of surgical candidates who visit ophthalmology practices for removal of cataracts are patients who have had prior refractive surgery. "It's difficult to determine their exact lens power," she said. "This is becoming a fairly common scenario as the RK patients (age and) become cataract patients." Indeed, IOL power calculation in eyes undergoing cataract surgery subsequent to myopic LASIK or photorefractive keratectomy can necessitate other measurement Clinician shares insights for identifying and helping patients who may have a challenging road to their vision goals O phthalmologists are increasingly faced with patients who have under- gone refractive surgery and are now presenting for cataract surgery, according to Sonia Yoo, MD, professor of oph- thalmology, Miller School of Medi- cine, University of Miami. Speaking at the 55th annual Walter Wright Symposium in Toronto, Dr. Yoo discussed how to steer clear of refractive "nightmares" in an ophthalmology practice. She explained that the best way to man- age unexpected refractive outcomes is to clearly inform patients who are at risk of having a poor outcome that it may be a challenging road Avoiding refractive nightmares Presentation spotlight

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