EyeWorld Korea June 2019 Issue

EWAP JUNE 2019 23 er (Gallilei, Ziemer Ophthalmic Systems AG, Port, Switzerland). The analyzer uses two rotating Scheimp- flug cameras and a Placido topogra- phy system to provide anterior and posterior segment measurements with good repeatability and re- producibility for both normal and post-refractive surgery corneas. Dr. Kim and colleagues eval- uated 109 patients (218 eyes; 98 femtosecond-LASIK eyes and 120 SMILE eyes). All eyes had < –6.0 D of myopia, < –3.0 D of astigmatism, > 280 μm residual bed thickness (RBT) for SMILE and >300 μm RBT for Femto-LASIK. The analyzer mea- sured CCT, anterior chamber depth, anterior and posterior K, anterior and posterior best fit sphere radius, and maximum posterior elevation (MPE). Their findings showed that SMILE tended to overestimate len- ticular thickness more than ablation depth for Femto-LASIK; the esti- mation of lenticular thickness thus needs to be revised through further investigations. They also found that changes in the posterior corneal sur- face were greater after Femto-LASIK than after SMILE in terms of MPE and posterior K. Risk management in SMILE Liang Gang, MD , who has been performing SMILE since 2012, shared her experiences with the procedure, highlighting surgical techniques and risk management. Reiterating the advantages of SMILE in terms of a surgical technique, Dr. Gang said that low suction provides more comfort for the patient and that lenticule sepa- ration and extraction translates to a stable and fast procedure. However, these also confer disadvantages in terms of a risk of suction loss and a steeper learning curve, respectively. Suction loss can be managed by restarting the procedure, either continuing SMILE or converting to LASIK. Partial suction loss can be managed by continuing the proce- dure or intentionally aborting. In either case, safety should be the first consideration. To help manage the learning curve, surgeons should start with flap making, familiarizing them- selves with docking, centration, and workflow. They also need to learn suction stability management and monitor for eye movements. Sur- geons should be alert for the signs thickness (CCT) of less than 490 to 500 μm is a relative contraindica- tion to LASIK. Seongjun Lee, MD , Daejeon, South Korea, evaluated the visual outcomes of SMILE, LASEK, and LASEK combined with corneal crosslinking (LASEK-CXL) as other options to correct myopia in eyes with thin corneas. Although LASEK may be a practical alternative to LASIK for thin corneas, SMILE has less biomechanical impact than surface ablation or LASIK. Cross- linking increases the biomechanical stability of the cornea. In their study, Dr. Lee and col- leagues found that SMILE, LASEK, and LASEK-CXL appear to be safe and effective for myopic correction in patients with thin corneas. How- ever, SMILE provided significantly better refractive predictability than LASEK and marginally better pre- dictability than LASEK-CXL (which was marginally better than LASEK). Also, the SMILE group had fewer postoperative complications and less induction of HOA compared with the LASEK and LASEK-CXL groups. SMILE and cyclotorsion- compensated wavefront- optimized PRK in myopic astigmatism Dalwoong Huh, MD , compared the astigmatic correction between SMILE and PRK with eye registra- tion in myopic eyes with > 0.75 D astigmatism. The SMILE group consisted of 277 patients (382 eyes), and the PRK group consisted of 250 patients (434 eyes). The groups were followed up to 1 year. By 1 year, Dr. Huh saw no statistically significant difference between the two groups in terms of visual acuity (no eye had a decrease in best spectacle-corrected visual acuity), spherical equivalent, refrac- tive cylinder, and predictability. He concluded that both SMILE and PRK with eye registration are safe, effec- tive, and provide predictable out- comes in treating myopic astigma- tism. SMILE had comparable results to PRK in treating astigmatism. Anterior segment changes after FS-LASIK and SMILE Evaluating the anterior segment changes after Femto-LASIK and SMILE, Bu Ki Kim, MD , used the dual-rotating Scheimpflug analyz- of suction loss, including a menis- cus forming along the edge and intrusion of the conjunctiva. The process of SMILE is rela- tively complicated, comprising four steps—lenticule cut, lenticule side cut, cap cut, and cap side cut. Suc- tion stability management also has different steps. Dr. Gang said that prevention and patient education are very important, with surgeons managing patient anxiety with what she called “verbal anesthesia.” In terms of lenticule extraction, surgeons should manage the cor- neal surface properly and maintain an appropriately moist cornea that is neither too dry nor too wet. Dr. Gang noted that an overly dry cornea leads to the formation of an opaque bubble layer, black spots, and overcorrection, while an overly wet cornea creates a higher risk of suction loss and potential undercor- rection. Surgeons also should reduce exposure of the corneal surface and reduce black spots and separation resistance for better visual recovery, Dr. Gang said. Vardhaman Kankariya, MD , Asian Eye Hospital, India, further expounded on the management of suction loss. He said that intraoper- ative complications during SMILE typically can be attributed to suc- tion loss during lenticule creation, most commonly resulting from patient eye contraction or sudden eye or patient movement but also possibly due to fluid entry through suction ports, chemosis, or small palpebral fissures. However, suction loss most commonly occurs during the cap cut. According to Dr. Kankariya, this is because as the lenticule is being formed, cavitation bubbles go from periphery to the center. As the bub- bles reach the center, the patient’s vision blurs, making the patient more anxious. The majority of patients respond to this by moving after the conclusion of lenticule cut has been completed—that is, during the cap cut. After suction loss, the VisuMax laser will automatically stop the treatment as a safety mechanism. A pop-up will show the number of steps completed and the number of steps left to complete and will ask the surgeon whether he or she would like to proceed. Clicking “yes,” a second pop-up shows the exact percentage completed in the step that was interrupted. The management will depend on the step that was interrupted: •Refractive lenticule cut – create a flap. •Lenticule side cut – either reduce the diameter of the lenticule by 0.1 or 0.2 mm and go about 20 μm deeper or create a flap. •Cap cut – redock and continue from the step that was incomplete, but maintain centration of new treatment. •Cap side cut (small incision) – redock and create small incision. Risk factors for suction loss include a small palpebral aperture, loose corneal epithelium, excessive reflex tearing, poor fixation, high corneal astigmatism, small white- to-white measurements, large cap diameter, patient anxiety, and the inability of a patient to follow instructions. It is important to communicate with patients and ensure they fully understand the procedure. During surgery, the surgeon should keep the contact glass clean, reduce tears in the conjunctival sac, and continue communicating with the patient, paying particular attention to smaller palpebral fissures, exces- sive squeezing of the eyelid, smaller corneal diameters, and conjunctival chemosis. A shorter duration of suction will decrease the risk for suction loss. Dr. Kankariya sees future devel- opments, such as a 1,000 kHz fem- tosecond laser, may further decrease the duration of suction. In conclusion, despite suction loss, good visual outcomes can be achieved with appropriate man- agement by redocking or simply proceeding with SMILE depending on the stage of suction loss. Coun- seling, risk factor identification, proper surface management, future improvements in the software, and higher-frequency femtosecond laser platforms will further decrease and prevent the risk for suction loss. Sponsored by Carl Zeiss Meditec Copyright 2019 APACRS. All rights reserved. The views expressed here do not necessarily reflect those of the editor, editorial board, or publisher, and in no way imply endorsement by EyeWorld, Asia-Pacific or APACRS. Sponsored by Carl Zeiss Meditec