EyeWorld India March 2017 Issue

EWAP refractive 47 March 2017 Five refractive surgery mistakes no surgeon should make by Stefanie Petrou Binder, MD EyeWorld Contributing Writer Top refractive surgeon warns against the most common and potentially damaging pitfalls in refractive surgery R efractive surgical guidelines are imperative to allow surgeons to treat within safe borders and ensure the best possible outcomes for their patients. The German Refractive Surgery Commission (KRC) is a common board of refractive surgical specialists of the Professional Association of German Ophthalmologists and the German Ophthalmological Society (DOG) that evaluates refractive surgical techniques and offers surgeons the much-needed and well-received guidelines and recommendations that help ensure highest quality standards and satisfied patients. Thomas Kohnen, MD , director and chairman, Department of Ophthalmology, Goethe- University, Frankfurt am Main, Germany, and KRC chairman (1.Vorsizender), presented his short list of refractive surgical mistakes at the 114th Congress of the DOG. Patient age and refractive stability The first two mistakes can be avoided through careful consideration of the patient’s age and refractive stability. As most refractive surgeons know, the first decisive restriction when considering refractive surgery is the patient’s age. In general, no one under 18 years of age should be considered for a refractive surgical procedure. That said, even before an individual can become eligible for a refractive procedure, refraction must be stable for at least 2 years. According to a paper published in 2014 by the KRC that set down refractive surgical guidelines, 1 the median age of patients whose vision had stabilized over 2 years and who underwent LASIK and phakic intraocular lens (PIOL) implantations was 33 years. “Performing refractive surgery too early in myopes is associated with regression and an increase in myopia,” Prof. Kohnen said. “High primary corrections then require retreatments, which are usually not possible using the same technique, and resorting to other techniques can be complicated. What you realize is that you should have chosen a different procedure from the start. Also, hyperopia can be underestimated in young patients. In the absence of cycloplegic examinations, young patients will accommodate when tested, and the magnitude of their hyperopia is not correctly assessed. Their surgeries amount to partial continued on page 48 treatments, and unfortunately retreatments make outcomes even worse because the optic zone in farsighted patients can’t be properly adjusted. We established in the KRC that when testing uncorrected and corrected visual acuity in hyperopic patients, subjective refraction is essential in patients under 45 years of age to rule out accommodative changes.” He elucidated that the surgical parameters set by the KRC included corrections of up to –8 D for myopes, up to +3 D for hyperopes, and up to –5 D astigmatism. These limits can be stretched to –10 D myopia, +4 D hyperopia, and –6 D astigmatism, after which good surgical outcomes become difficult to achieve. The upper limits are further defined by the combined upper limits of each measurement, for instance an eye with +4 D sphere and –6 D cylinder or –4 D sphere and +6 D cylinder is borderline. Similarly, 0 D sphere and +6 D cylinder or +6 D sphere and –6 D cylinder are outside of the acceptable limit. Going beyond these limits is likely to cause more trouble than good and needs to be weighed accordingly. False promises According to Prof. Kohnen, the third mistake no surgeon should blunder into is promising a patient something that cannot be delivered. “False promises are important to avoid, as they influence the patient’s level of satisfaction. We try in refractive surgery to make the patient spectacle-free. This may be possible in a 30-year-old, nearsighted patient, but even that patient will need a pair of glasses down the line in 20 years, when presbyopic changes occur. Furthermore, the patient should be made aware of factors that can influence surgical outcomes, such as post- surgical residual error. There are too many brochures and internet sites promising complete spectacle independence, and patients need to be made aware that these may not be true,” Prof. Kohnen said. A study that investigated wavefront aberrations and subjective optical quality (SOQ) showed that SOQ after uncomplicated LASIK was partially explained by postoperative wavefront errors. 2 In another study that evaluated the 5-year efficacy of a PIOL in 515 eyes with moderate to high myopia, in spite of very good results with respect to BCVA and loss of lines, the predictability was less than desirable with 67% of eyes within ±1 D. 3 In other words, in spite of the overall great visual outcomes using LASIK and other refractive surgical procedures,