Clinical Outcomes of Immediate Reapplication of Small Incision Lenticule Extraction Without Adjustment of Surgical Parameters After Loss of Suction

This was a paired eye retrospective observational case series conducted at B&VIIT Eye Center, Seoul, Republic of Korea. The study protocol followed the principles of the Declaration of Helsinki and good clinical practice. The institutional review board at Yonsei University College of Medicine approved the study, and the same institutional review board waived the informed consent requirement because it was a retrospective study. All patients underwent SMILE between January 2017 and March 2019. All surgeries were performed by two experienced surgeons (IHR and ISL). Patients who underwent uneventful SMILE in one eye (the Uneventful group) and immediate reapplication of SMILE without adjustment of surgical parameters following loss of suction in the contralateral eye (loss of suction group) were included.

Inclusion criteria included age 20-45 years, stable myopia for ≥ 1 year, corrected distance visual acuity (CDVA) of 20/25 or better, spherical equivalent refraction (SEQ) of −2.00 at −8.00 diopters (D), and refractive astigmatism of

Patient assessment

All examinations were performed before and 6 months after surgery. Patient assessments included measurement of logarithm of minimum angle of resolution (logMAR), uncorrected distance visual acuity (UDVA), CDVA, overt refraction, slit lamp examination (Haag-Streit , Köniz, Switzerland), central corneal thickness (CCT), and Scheimpflug-based corneal tomography (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany). Corneal wavefront aberrations were assessed using a Pentacam HR in a 6mm area.

Surgical technique

Uneventful SMILE (Eventless Group)

SMILE was performed using a VisuMax 500 kHz system (software version 2.4.0; Carl Zeiss Meditec AG, Jena, Germany) with standardized techniques17. The spacing of the laser dots was set at 4.5 μm. The upper and lower edges of the refractive lenticule were delineated and a 2 mm incision was made at the 145° meridian. Once the upper and lower interfaces were separated, the lenticule was extracted using microforceps. The diameter of the cap was between 6.7 and 7.8 mm. The diameter of the optical zone was between 5.7 and 6.8 mm. The expected thickness of the cap was 90 to 135 μm. The default cap thickness has been set to 120 μm. The thickness of the cuff was modified according to the residual stromal thickness, the degree of refractive correction and the preoperative pachymetry. Postoperative medications included 0.5% moxifloxacin and 1% prednisolone four times daily for 1 month.

Immediate reapplication of SMILE after loss of suction (loss of suction group)

When a loss of suction occurred while cutting the posterior surface of the lenticule, the SMILE procedure was repeated from the beginning. The surgical parameters were re-entered without modification. When a loss of suction occurred during or after cap cutting, the SMILE procedure was repeated from the point at which it was stopped. In these cases, the surgical parameters did not need to be re-entered into the laser control platform.

statistical analyzes

Statistical analyzes were performed using IBM SPSS Statistics for Windows, version 25.0 (IBM Corp., Armonk, NY, USA). The Kolmogorov-Smirnov test was used to confirm the normality of the data. Two measures were compared using the paired t-test for normally distributed data or the Wilcoxon signed rank test for non-normally distributed data. Categorical variables were compared using the chi-square test and linear regression analysis was used to investigate the predictability of refraction. All data are presented as mean ± standard deviation. Statistical significance was set at P

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