Eyeworld

EW REFRACTIVE 56 February 2018 Research highlight by Maxine Lipner EyeWorld Senior Contributing Writer they found that while the average astigmatism only changed from 1.1 D to 0.92 D postoperatively, there were three eyes that increased 1 D or more in the amount of astigmatism. "We found there was an axis shift in the astigmatism anywhere from 1 to 70 degrees," Dr. Terry said. "That's big because 30% of the eyes had more than a 30-degree shift in their astigmatic axis after DMEK." What's more, 25% had between a 20- and 30-degree shift, which means that 55% of eyes will experience a shift in astigmatism. That's important because if you place a toric lens in one of these patients, you may ultimately be off. If the preoperative astigmatism is at 90 degrees and you put the toric lens in at 90 degrees as you think you should, 6 months later the toric lens is still at 90 degrees but you may find the corneal astigmatism axis is now at 120, leaving the patient with some residual astigmatism. Takeaway messages Dr. Terry thinks there are several messages from the study. "One take- home message is that it's OK to do triple procedures in eyes that have had previous refractive surgery," Dr. Terry said, adding that it is possible to get good results in these patients, with study results indicating that 65% were 20/20 or better after triple surgery and 90% were 20/25 or better. "However, in all of these eyes we put in a lens that was not a toric lens and not a multifocal lens," he said. "We were glad we did because with 30% of those eyes changing their axis of astigmatism, if we had tried to put a toric lens in to correct their astigmatism, we would have been wrong 30% of the time." Likewise, if you put in a multi- focal lens, you have to be aware of a large range of myopic and hyperopic shift that can occur that will affect the postoperative satisfaction of the patient, Dr. Terry noted. In patients who have previously undergone refractive surgery, such as this cohort, this can be particu- larly important. "We were studying patients who had a mindset for re- fractive error because all of those pa- tients had undergone PRK or LASIK, so they wanted to have great vision without glasses," he said. "You are dealing with a population of people that is tuned in to what they want, DMEK-only group, investigators found that there was no signifi- cant change in the mean spherical equivalent. "They went from a mean spherical equivalent of 0.41 D pre- operatively to a mean postoperative value of 0.7 D," Dr. Terry said. However, investigators found that while the mean didn't shift significantly, there was a range of outliers. "There was a range of changes in phakic cases between a –0.63 myopic shift and a hyperopic shift of +1.5 D," Dr. Terry said, add- ing that this is important because the assumption is that you're going to get a hyperopic shift. Although you do get a mean hyperopic shift of about 0.3 D, the problem is the range is so high, varying from a shift of 0.5 D of myopia to up to 1.5 D of hyperopia. "That means it's not as predictable in the entire series if you have a range that big," Dr. Terry said. "You don't have the predict- ability of corneal power that you would have doing simple cataract surgery in a virgin eye where you're not changing the overall edema with a DMEK." Astigmatism was another con- sideration here. When investigators looked at the topographic data, LASIK. Of these, 20 were treated for Fuchs' dystrophy and one eye was treated for endothelial failure from suspected herpes simplex uveitis, Dr. Terry said. After undergoing either DMEK alone or in a triple proce- dure, with DMEK in conjunction with cataract extraction and IOL replacement, investigators found that patients attained good results. "The uncorrected visual acuity after surgery averaged 20/38," Dr. Terry said. This was an improvement from the mean preoperative uncorrected visual acuity of 20/58. The best corrected visual acuity improved from a mean of 20/30 to 20/23. "Some of the eyes were phakic and had the crystalline lens in place, some of them were pseu- dophakic, and some of them we did triples on," Dr. Terry said, adding that there was no difference in the results in any of those subgroups, with all patients doing well. Investigators also wanted to determine if they had changed the overall focusing power of the cornea. "We looked at just the cases that had only DMEK and nothing else," he said. "We removed the data from any eye that had DMEK and cataract surgery done." In this DMEK after PRK or LASIK I n a recent study published in Cornea, investigators considered how those who had previously undergone refractive surgery fared when undergoing DMEK, according to Mark A. Terry, MD, director of corneal services, Devers Eye Institute, Portland, Oregon. 1 Years ago when PRK and LASIK were approved, extreme Fuchs' dys- trophy wasn't even recognized, Dr. Terry pointed out. "Those folks are now 50 years old and their Fuchs' dystrophy is becoming manifest," he said, adding that now they have corneal swelling or edema from their Fuchs' and need to have DMEK sur- gery, leaving the practitioner with the conundrum of what to do with a LASIK flap that has swelling. It was a question of whether practitioners could trust topography and tomog- raphy readings and treat the patient the same way as those who had not previously undergone refractive surgery. Studying post-refractive DMEK The study included 21 eyes that had previously undergone either PRK or Avoiding transplant travails Eye 1 week after DMEK under PRK. The vision was 20/25 without glasses. Source: Mark A. Terry, MD

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