Accuracy and precision of cap thickness in small incision lenticule extraction

AIMS: To report and compare the cap thickness predictability of small incision lenticule extraction (SMILE) and flap thickness of femtosecond laser-assisted in situ keratomileusis (femto-LASIK). SETTINGS AND DESIGN: Beyoglu Eye Training and Research Hospital, Refractive Surgery Department, Istanbul, Turkey. Retrospective pilot study. MATERIALS AND METHODS: Medical records of patients who had SMILE in one eye and femto-LASIK in the other eye were reviewed. Visante corneal Optical Coherence Tomography (OCT) images at 1 week and 1 month post-surgery were analyzed. Both cap and flap thickness at the temporal edge and the nasal edge were measured and compared to each other. STATISTICAL ANALYSES USED: PAWS Statistics 18 and unpaired student t-test were used to compare the groups. RESULTS: The study included 66 eyes of 33 patients (24.7 ± 3.8 years, 20 females and 13 males). Mean flap thickness was 114.88 μm ± 4.96 μm, and mean cap thickness was 114.63 μm ± 5.18 μm. In group 1 (SMILE), cap thickness values were 115.84 μm ± 6.84 μm, 114.75 μm ± 7.36 μm, 113.66 μm ± 6.88 μm, and 114.27 μm ± 6.90 μm in measurement zones 1, 2, 3, and 4, respectively. In group 2 (FemtoLASIK), flap corneal thickness values were 115.96 mmHg ± 7.01 mmHg, 114.72 mmHg ± 7.17 mmHg, 113.54 mmHg ± 6.45 mmHg, and 115.30 mmHg ± 6.64 mmHg in measurement zones 1, 2, 3, and 4, respectively. In both groups, no statistically significant change within the measurement zones was observed. CONCLUSION: The predictability of cap thickness in SMILE surgery does not differ from the femto-LASIK flaps created using the same femtosecond laser platform.