Eyeworld

EW REFRACTIVE 60 July 2018 Research highlight by Maxine Lipner EyeWorld Senior Contributing Writer that risk fit an exponential model," he said, adding that the model they created could be used to derive the relative risk of developing striae as a function of the patients' preopera- tive spherical equivalent. "I know that a patient who's treated for –10 D of myopia is 6.8 times more likely to develop striae than a patient who is treated for –2 D of myopia. That's useful informa- tion for a surgeon to know to offer detailed informed consent to the patient and to plan surgical care," he said. Investigators found that the amount of time that passed since the LASIK procedure was complet- ed was important. "Almost 10% of striae are detected in the first hour after surgery," Dr. Wallerstein said. "That tells us we need to keep our patients around because this process of the flap not adhering complete- ly and shifting occurs in the first few hours." A simple change such as keeping patients an extra hour in clinic will allow practitioners to detect and immediately treat 10% of all striae cases, he noted. In addition, the study addressed the idea that striae might induce some cylinder. However, this was not necessarily what investigators detected, Dr. Wallerstein observed. "We found that on average striae caused a mild hyperopic shift and that the majority—77%—don't induce any astigmatism," he said, adding that there is variability based on where the striae are located. Those located closer to the central visual axis might induce cylinder, and if they're off-axis they might in- duce some higher order aberrations that contribute to decreased visual quality. Investigators also learned that while striae can cause patients to lose between one and three lines of vision, treatment can usually correct this. The efficacy index improves by 25%, heightening the accuracy to close to the non-striae eye and al- lowing the safety index to return to that of the non-striae eye. However, there still may be a slight difference. "We found that 12% of those striae- treated eyes had one line or more of New findings Investigators learned a variety of things about striae. Prior to the study, the reported striae incidence varied between 0% and 13%. "In the large database that our study looked at, the incidence is 0.79%," Dr. Wallerstein said. "That number is a true incidence, since it comes from more than 100,000 LASIK surgeries." Knowing this can help improve informed consent and patient care, he pointed out. One piece of new information investigators learned was that 23.5% of cases were bilateral. Dr. Waller- stein hypothesized that the reason that some patients develop bilateral striae may be an anatomical predis- position and host related. When investigators considered potential factors that might predis- pose patients to striae, they deter- mined that preoperative spherical equivalent and total ablation depth were the most significant risks, Dr. Wallerstein reported. "We found case-controlled series were 109,403 eyes that had undergone LASIK surgery in a multi-surgeon, multi- center practice. First, investigators determined the incidence and the risk factors for clinically significant post-LASIK striae, then looked at outcomes, Dr. Wallerstein noted. "For the ones that needed an inter- vention, we reported the outcomes both before we lifted the flap and irrigated and after the treatment was done," he said. "Then we compared those to the non-striae contralateral eyes." Dr. Wallerstein pointed out that all the surgeons included in the study received the identical training in order to work under the umbrella of this multicenter practice. This meant that identification of patients with postoperative striae as well as postoperative removal was standard- ized, he stressed, adding that this makes the validity of the data even stronger. The latest on clinically significant flap striae F lap striae can mar an otherwise successful LASIK procedure. Recent research published in the Journal of Cataract & Refractive Surgery 1 pegs the true incidence of this at 0.79% of cases that require interven- tion and considered risk factors and patient outcomes, according to Avi Wallerstein, MD, assistant professor of ophthalmology, McGill Universi- ty, Montreal, Canada. Investigators thought that since flap striae is the most common early postop LASIK complication, this was important to study further. "This is part of a refractive surgeon's day-to- day practice, so it's important to get granular and further understand it,'" Dr. Wallerstein said. Large study pool Included in the retrospective A wrinkle in LASIK Microstriae Source: Avi Wallerstein, MD

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