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.