FEATURE 14 EWAP MARCH 2023 Dr. Rostov said that SMILE has similar criteria as LASIK and PRK. SMILE is approved for up to 3 D of astigmatism. “I find that above 2.0–2.25 D, when it gets to the higher amounts of astigmatism, in my practice LASIK does a better job.” She added that if the patient has a small superficial scar within the SMILE treatment zone, she will choose LASIK because you need a pristine cornea with SMILE. “You can’t have any scars or opacities within the treatment zone, and the reason is that the femtosecond laser is not able to go through opacities.” Dr. Rostov noted that she might choose LASIK instead of SMILE for smaller prescriptions because the lenticule would be very thin in these cases and might be harder to dissect. You could do it, but it depends on the patient. “Especially if it’s a thicker cornea and very low prescription, I might do LASIK instead,” she said. Dr. Rostov agreed that there may be complications that come up, as with any procedure. She had one case where she was unable to get the lenticule out, and she proceeded with PRK. Another potential complication is a suction break. Dr. Rostov said to try to prevent this, she might use medications or “verbal anesthesia.” “I tell patients to listen to my voice. I tell them ahead of time what to expect. I tell them just to listen to what I’m saying and to hold as still and be as quiet as possible,” she said, adding that she’ll let patients know when it’s particularly important to be very still. Dr. Rostov has only had a handful of suction breaks in more than 1,000 cases, and they occurred late in the procedure. With SMILE, there are four cuts that the laser does. The first is the refractive cut. “If you get a suction break during the refractive cut, you cannot do SMILE,” she said. The second cut determines the thickness of the lenticule. The third is the cap, which is the top of the lenticule and is a non-refractive cut. Dr. Rostov has experienced suction breaks during the cap cut. “You can redock and redo it,” she said, and in her cases, the procedure was still successful. There could also be problems during lenticule dissection, Dr. Rostov said. “If the epithelium is irregular or you have too much meibum on the surface, you can get ‘black spots,’ which are places where the laser is not going to be able to go through,” she said. “When you see the laser pattern, you’ll notice these spots where there was meibum or something like that, and if there’s too much, that will make the lenticule dissection too difficult.” Dr. Rostov has not experienced this complication in her SMILE cases Iagree with Dr. Kugler that LASIK performs better than SMILE in patients with very low myopia. I disagree with Dr. Kugler that LASIK is easier to enhance than SMILE. The SMILE circle program is easy to use, and has a much lower incidence of epithelial ingrowth than relifting the flap (Chang et al. 2022). However, creating a LASIK flap with the circle program will cost more than relifting the flap. If I’m concerned that the patient is likely to lose suction, I make my spot separation and line separation wider, which speeds up the laser by a few seconds. A few seconds may not seem to be significant, but it could feel like an eternity especially when the patient appears to be moving. The key is to get the lenticule and the side cut performed as quickly as possible. Giving the patient some oral tranquillizer helps a lot, too! I also warn the patient (preoperatively) that if SMILE fails, we may have to convert to LASIK. For the novice SMILE surgeon, I recommend using closer spot and line separation to make the dissection much easier. The laser will take longer to perform, but there will be fewer lenticule and cap complications. To prevent black spot, we have a suction tube set up in the operation room, and I copiously wash the eye with BSS. I have only had one eye with black spots, and vision was 20/20 on POD 1. I also wash the interface after lenticule extraction and I only had one mild DLK out of the 2,703 SMILE eyes. The biggest advantage of SMILE is obviously the absence of flap and flap trauma. I had one patient who had LASIK surgery over 10 years ago, he came back to me due to traumatic flap dislocation, which will not occur in SMILE patients. However, I repositioned the flap and he did not lose any vision. Regarding suction breaks, I agree with Dr. Rostov that most suction breaks occur late in the procedure. We are currently using the new VM800 (SMILE PRO). The entire laser procedure lasts from 10 to 14 seconds compared to the older laser which takes 22 seconds. A faster laser time leads to a shorter suction time and reduces the risk of suction loss. The new laser is four times faster and it allows closer spot separation and therefore easier separation, reducing the risk of lenticule/cap tear and epithelium ingrowth. Reference 1. Chang JSM, et al. Effect of time since primary laser-assisted in situ keratomileusis on flap relift success and epithelial ingrowth risk. J Cataract and Refractive Surg. 2022;48(6):705–9. Editors’ note: Dr. Chang receives lecture honoraria and research grants from Alcon and Carl Zeiss, and a lecture honorarium from Global Vision HK Ltd. John Chang, MD Hong Kong Sanatorium & Hospital 8/F, Phase II, Li Shu Pui Block, Hong Kong john.sm.chang@hksh.com ASIA-PACIFIC PERSPECTIVES continued on page 20
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