Eyeworld

EW FEATURE 46 Keratorefractive surgery August 2015 by Rich Daly EyeWorld Contributing Writer guided refractive systems, but new wavefront sensors are much more robust. We will need to see head-to- head trials for these more sophis- ticated wavefront-guided systems that base treatments on the optics of the eye versus topography-guid- ed ablation," Dr. Koch said. "But it will be helpful to have both of these technologies available." Dr. MacRae agreed that topog- raphy-guided refractive surgery is a therapeutic option, as opposed to a first-line alternative to existing systems. It might prove especially useful in eyes with corneal irregular astigmatism or keratoconus. "It's a nice backup option for them," Dr. MacRae said. Stronger corneas? Future precautionary uses for col- lagen crosslinking in primary laser vision procedures may include any patient where a fragility of the cornea that would predispose him/ her to ectasia is suspected, Dr. Koch said. "We may learn that we can expand our indications for LASIK by pretreating or treating these patients at the time of ablation," Dr. Koch said. "There are patients that we are reluctant to treat because of suspect- ed or early keratoconus, and those patients are showing good results with a combination of crosslinking and primary surface ablation." incision to separate the lenticular interfaces and allow the lenticule to be removed, thus eliminating the need to create a flap. The international results and the unpublished preliminary U.S. clinical trial results are quite good, especially for low corrections with limited amounts of astigmatism, said Coleman Kraff, MD, direc- tor of refractive surgery, Kraff Eye Institute, Chicago. Potential benefits of SMILE are the relatively high- er biomechanical strength of the remaining cornea and a reduction in the variability of the biomechanical effects produced by refractive tissue removal. However, there are some trade-offs involved with the SMILE procedure. For instance, surface ablation is required for enhance- ments, which eliminates one of its primary advantages. "Initially it may be touted as a less invasive procedure, but if pa- tients end up with PRK retreatment, they're not going to regard that as very successful in terms of meeting their expectations," said Scott M. MacRae, MD, professor of ophthal- mology and visual science, Universi- ty of Rochester, Rochester, N.Y. "We need to be cautious about what type of expectations we create." Dr. MacRae noted that some presented data has indicated that SMILE is more successful in patients with high myopia by leaving fewer higher order aberrations. However, the lack of peer-reviewed published data has left it unclear whether SMILE actually provides superior dry eye results compared to laser vision correction. Other unanswered questions include how to finish the case if suc- tion is lost in the coupling suction applied to the peripheral cornea, Dr. Kraff said. He also emphasized the need to discuss the technology's limitations with the patient ahead of time, due to its differences with traditional laser vision correction procedures. "There may be some patients who perceive that since there is no flap it is safer, but the jury is still out on that," Dr. Kraff said. Therapeutic option The emerging technology of topog- raphy-guided refractive surgery is expected to find a place in the prac- tice of Douglas D. Koch, MD, pro- fessor and the Allen, Mosbacher, and Law chair in ophthalmology, Cullen Eye Institute, Baylor College of Medicine. However, because wave- front-optimized and wavefront-guid- ed ablations provide excellent out- comes in normal corneas, the role for topography-guided procedures is likely limited to extreme cases, particularly patients with primarily irregular astigmatism. "There are patients you can't capture with regular wavefront- Emerging technologies aim to expand refractive treatment Monthly Pulse Keratorefractive surgery T he topic of this Monthly Pulse survey was "Keratorefractive surgery." We asked, "In your opinion, how important is it to consider the posterior corneal astigmatism for a toric IOL?" More than half of respondents to this survey answered, "Important but not necessary to routinely measure as it can be accounted for by a population-based adjustment." When asked about the percentage of cataract patients in which they currently implant a toric IOL, the majority said 6 to 15%. The maximum amount of postoperative manifest astigmatism that the majority of respondents to this survey would consider acceptable after a premium IOL is 0.50 to 0.75 D. Finally, we asked, "What is your primary technique to assist in toric IOL alignment?" The majority answered limbal marks placed prior to the procedure. Newer refractive treatments are showing promise A growing number of refractive options aim to expand treatment beyond what is currently possible with laser vision correc- tion and without some of the side effects of the established technology. However, there are important limitations to consider with some of the new options, even when the newer technologies show great potential. Unanswered questions Small incision lenticule extraction (SMILE, Carl Zeiss Meditec, Jena, Germany) was developed as an alternative to traditional LASIK and PRK. The procedure involves passing a dissector through a small 2–3 mm AT A GLANCE • International SMILE results are good, but the procedure comes with some tradeoffs. • Topography-guided refractive surgery may be limited to extreme cases. • Collagen crosslinking could expand indications for LASIK, but more research is needed. In your opinion, how important is it to consider the posterior corneal astigmatism for a toric IOL? Very important and should be routinely measured Important but not necessary to routinely measure as it can be accounted for by a population-based adjustment Not important

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