Eyeworld

EW REFRACTIVE 38 February 2017 by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer 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, outliers exist that may necessitate retreatment. This reality needs to be communicated to pa- tients to adjust their expectations or they will be unsatisfied. Not enough facts on new procedures New procedures in refractive surgery require evaluation. According to Prof. Kohnen, "When new tech- niques reach the market, they need to be tested. We try to do this in Germany in the KRC, to determine how safe and effective new pro- cedures really are. We look at safe inclusion criteria, need for retreat- ment, and complications." One of the more recent arrivals among refractive surgical tech- niques, ReLEx SMILE (Carl Zeiss Meditec, Jena, Germany), which treats nearsightedness intrastromal- ly and involves lenticular removal, has been put on the same level as LASIK and PRK by the KRC, due to its outcomes. The procedure is best when performed for myopic correc- tions from –3 D to –8 D and astig- matism corrections of up to 5 D, Prof. Kohnen said. But this does not preclude complications following this procedure, in some cases. According to a Danish cohort study that implemented SMILE in 922 healthy patients (1,800 eyes) with myopia or myopic astigma- tism between January 2011 and March 2013, 86% (1,346 eyes) had unchanged or improved CDVA, and a loss of two or more lines was observed in 1.5% of eyes. 4 Compli- cations from this study included retreatments in 13 eyes, 8% haze, epithelial dryness on the first postop day in 5%, and others. "The results were not as good as what has been achieved in modern femtosecond laser surgery, plus there were some complications, among which one in particular needs to be discussed in reference to this pro- cedure: a small, decentered optical zone. This will not always present itself until after the surgery, when 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 re- fractive 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 oc- cur. 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 wave- front aberrations and subjective op- tical quality (SOQ) showed that SOQ after uncomplicated LASIK was par- tially explained by postop wavefront errors. 2 In another study that eval- uated 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 retreatments, which are usually not possible using the same technique, and resorting to other techniques can be complicated. What you real- ize is that you should have chosen a different procedure from the start. Also, hyperopia can be underes- timated 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 treatments, and unfortunate- ly 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 my- opes, 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 astigma- tism, after which good surgical out- comes 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 cylin- der or –4 D sphere and +6 D cylinder is borderline. Similarly, 0 D sphere and +6 D cylinder or +6 D sphere Top refractive surgeon warns against the most common and potentially damaging pitfalls in refractive surgery R efractive surgical guide- lines are imperative to allow surgeons to treat within safe borders and ensure the best possi- ble outcomes for their patients. The German Refractive Surgery Commission (KRC) is a 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 the highest quali- ty standards and satisfied patients. Thomas Kohnen, MD, PhD, FEBO, professor and chair, Department of Ophthalmology, Goethe-University, Frankfurt am Main, Germany, and KRC chairman, 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 avoid- ed 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. Accord- ing to a paper published in 2014 by the KRC that set down refractive sur- gical 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 Five refractive surgery mistakes to avoid Presentation spotlight continued on page 40

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