Eyeworld Supplements

EWAP SUM 2017 - Sponsored by Carl Zeiss Meditec

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The news magazine of the Asia-Pacific Association of Cataract & Refractive Surgeons Sponsored by Carl Zeiss Meditec Taking Vision Further: Update on Innovative Refractive and Cataract Solutions Laser Vision Correction — Today and Tomorrow A lunch symposium sponsored by ZEISS (Carl Zeiss Meditec, Jena, Germany) during the 2017 Asia-Pacific Academy of Ophthalmology (APAO) meeting highlighted "Laser Vision Correction – Today and Tomorrow." The session was moderated by Khairidzan Mohd Kamal, MD, Kuala Lumpur, Malaysia. Marcus Ang, MD, Singapore, Cynthia Roberts, PhD, Columbus, Ohio, Jodhbir Mehta, MD, Singa- pore, and Sri Ganesh, MD, Ban- galore, India, focused their presen- tations on topics related to small incision lenticule extraction (SMILE). Dr. Roberts discussed the biomechanics of SMILE and the U.S. Food and Drug Administration results. She highlighted information about general biomechanics and the biomechanical response to refractive surgery. Dr. Roberts discussed two studies. The first was a theoretical study of a finite element comparison of LASIK vs. SMILE, which didn't use actual clinical parameters. She explained that the same diameter SMILE cap and LASIK flap size were used in the study and the same cap/ flap thickness were used as well, although this is different than what would be done in the clinical setting. In comparing a postoperative "ideal cornea" (postop geometry with no change in properties) to the SMILE and LASIK outcomes, Dr. Roberts said that the SMILE eye was closer to the idealized postoperative stress distribution because the cap can car- ry some stress and cause less of an increase in the residual stromal bed stress. "When you compare SMILE to LASIK, there's biomechanical dis- tribution in SMILE similar to the ideal case," she said. She discussed a flap vs. cap contralateral study of 10 eyes of five patients. The patients had SMILE in one eye and femtosecond lenticule extraction (FLEx) in the fellow eye. These provided a good comparison, she said, because the SMILE eye had a cap, while the FLEx eye had a flap, and both used the same mechanism for tissue removal. Preoperative and postoperative tomography continued on page 2 were examined, and the study used inverse finite element analysis to determine what change in properties had to occur for the postoperative map to be produced, given the tissue removal. FLEx produced a 49% (range 2–87%) greater mean reduc- tion in stromal collagen fiber stiffness within the flap region than contralat- eral cap region in SMILE, Dr. Roberts said. There were lower stresses and deformations within the residual stromal bed in SMILE eyes. Looking at the results of what happened when IOP was changed in the model, the FLEx eye with a flap had a greater displacement of residual stromal bed at both IOP levels that were analyzed than SMILE, she said. Dr. Roberts cautioned that the major biomechanical impact of any refractive surgery is tissue removal, and cap vs. flap is a secondary ef- fect. SMILE weakens the cornea less than LASIK, but the preop cornea is still stronger than both, she said. Do not perform SMILE if you suspect an "at risk" cornea, she said. Surgeons need to follow the same general guidelines of laser vision correction for SMILE as they are currently following for LASIK. Dr. Roberts also discussed the FDA results for SMILE (although she noted that she was not involved in the study) from the prospective, multi- center, open-label, single-arm study. In the study, 336 eyes were treated at five sites in the U.S. There was unilateral treatment with 12-month follow-up, and the study data were submitted when 300 eyes reached 12 months. She highlighted specif- ic inclusion criteria and exclusion criteria. The study showed a higher percentage of patients with postoper- ative UCVA greater than preoperative BSCVA (70% at 6 months and 74% at 12 months). The study had excellent effectiveness outcomes, Dr. Roberts said. Carl Zeiss Meditec announced that it received U.S. FDA approval for the ReLEx SMILE procedure. With FDA approval, surgeons can now perform SMILE for the correction of myopia in the U.S. Dr. Ganesh discussed his experience as a doctor and patient with PRESBYOND laser blended vision. He shared details of his own APACRS Supplement to EyeWorld Asia-Pacific Summer 2017 SMILE procedure Source: Cynthia Roberts, PhD Finite element comparison of LASIK vs. SMILE. Sinha Roy A, et al. Comparison of biomechanical effects of small-incision lenticule extraction and laser in situ keratomileusis: finite-element analysis. J Cataract Refract Surg. 2014;40:971–80. Source: Cynthia Roberts, PhD

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