EyeWorld Asia-Pacific December 2020 Issue

collagen reflected in imaging. When comparing preoperative imaging in surgeries with LASIK, SMILE, and PRK to postoperative (3 months), it can be seen that both SMILE and PRK maintain a lot of integrity of the cornea in terms of collagen structure. In Dr. Shetty’s own research, he studied the biomechanics of LASIK flap and SMILE cap and assessed collagen imaging after both surgery with LASIK and SMILE. The results showed that there was a huge drop in the biomechanics and collagen, but the imaging after both procedures were similar. Dr. Shetty also found that a gene analysis preoperatively matched the collagen mapping, thus showing that collagen imaging is quite accurate. SMILE Xtra: My Take Dr. Sheetal Brar next presented on SMILE Xtra and its techniques. Dr. Brar introduced suspect topogra- phies including inferior steepening, on SMILE). Looking at the different options, surface ablation after SMILE may be the simplest, safest, and most straight-forward retreatment proce- dure, especially in patients whose cornea needs to be biomechanically protected. The downside in surface ablation, apart from pain, is that there are more inflammatory responses after a surface ablation following the SMILE procedure than a primary surface ablation. Dr. Sachdev recom- mended a 0.02% mitomycin C for 20 to 30 seconds. Regarding the results of surface ablation after SMILE, Dr. Sachdev described it as “gratifying.” Though individual recovery may be longer than the flap method, it is important to note that the tissue-sav- ing method provided good results, whereas enhancement with the aspherically optimized profile resulted in overcorrection. Thin flap LASIK post-SMILE is recommended for patients with a thick cap because of the clear zone between the epithelium and the cap. This is because if one has too many interfaces, gas bubbles may migrate to the interfaces, causing unwant- ed slivers of tissue. Thin flap LASIK post-SMILE does give good out- comes, though one has to be aware that inflammation rate may be higher. In cap-to-flap procedures, the cap of the primary surgery with SMILE is converted into a full flap. Patients who undergo this procedure often re- port no pain and a speedier recovery, although the procedure as a whole may be counterintuitive in enhancing a flapless procedure with a flap. Imaging the Collagen and its Impact on SMILE Surgery The next presentation was given by Dr. Rohit Shetty on “Imaging the Collagen and its Impact on SMILE Surgery.” Dr. Shetty began by dis- cussing how the wavelength of light typically used in imaging is not very suitable for imaging collagen. Meek et al. 4 studied the use of x-ray scattering techniques to image collagen and it was found that in a normal eye, one can see the darker colors on imaging representing tighter bound fibers with the four zones in the corner of the eyes. When a suspect eye was im- aged, the coloring of the tightly bound fibers is weakened along with poor corneal biomechanics (See Figure 3). In keratoconus, there is no healthy I/S asymmetry (> 1.4 D), posterior elevation, thin pachymetry, and steep corneas that can potentially be man- aged with a new modality: corneal refractive surgery plus accelerated cross linking (Xtra procedures). In Dr. Brar’s research, she reported a good safety and efficacy profile with SMILE Xtra procedures. However, surgeons may hesitate to utilize this procedure due to unclear eligibility criteria, an unstandardized cross-linking pro- tocol, potential side effects of haze, hyperopic shift and corneal flattening over a long-term period, and in- creased overall cost (See Figure 4). Speaking to eligibility criteria, Dr. Brar considered patients eligible for SMILE Xtra if they have high myopia or myopic astigmatism, borderline corneal thickness (480 microns or less), suspect topography, age less than 30 years old, atopy, and/or kera- toconus in one eye. In a retrospective study by Dr. Brar, 4,630 eyes were studied with 3,932 normal topogra- phy eyes undergoing SMILE. Out of the 3,932 eyes, only 2 eyes (0.05%) experienced ectasia. In eyes with border topography undergoing SMILE Xtra (522 eyes), none experienced ectasia while 5 eyes out of 176 eyes (2.84%) undergoing SMILE experi- enced ectasia. Dr. Brar concluded that SMILE Xtra is safe and effective for prophylaxis of corneal ectasia in borderline corneas. Additionally, there is anecdotal evidence that the biomechanics with SMILE Xtra may be better compared to SMILE alone, though further data is necessary to validate these results. References: 1. Sambhi RS et al. Can J Ophthalmol 2020 2. Lee JB et al. J Refract Surg 2000 3. Schallhorn JM et al. J Refract Surg 2019 4. Meek KM et al. Prog Retin Eye Res 2009 Figure 4. SMILE Xtra at 24-month follow-up shows significantly higher postoperative corneal resistance factor (CRF) compared to traditional surgery with SMILE. Source: Ganesh S et al. Indian J Ophthalmol 2018 Media placement sponsored by Carl Zeiss Meditec AG Not all products, services or offers are approved or offered in every market and approved labeling and instructions may vary from one country to another. The statements of the authors of this supplement reflect only their personal opinion and experience and do not necessarily reflect the opinion of Carl Zeiss Meditec AG or any institution with whom they are affiliated. Carl Zeiss Meditec AG has not necessarily access to clinical data backing the statements of the authors.The statements made by the authors may not yet been scientifically proven and may have to be proven and/or clarified in further clinical studies. Some information presented in this supplement may only be about the current state of clinical research and may not be part of the official product labeling and approved indications of the product.The authors alone are responsible for the content of this supplement and any potential resulting infringements resulting from, in particular, but not alone, copyright, trademark or other intellectual property right infringements as well as unfair competition claims. Carl Zeiss Meditec AG does not accept any responsibility or liability of its content. EN_34_021_0063I