Accuracy and precision of cap thickness in small incision lenticule extraction

Abstract

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 femtoLASIK in the other eye were reviewed. Visante corneal Optical Coherence Tomography (OCT) images at 1 week and 1month 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 mu m +/- 4.96 mu m, and mean cap thickness was 114.63 mu m +/- 5.18 mu m. In group 1 (SMILE), cap thickness values were 115.84 mu m +/- 6.84 mu m, 114.75 mu m +/- 7.36 mu m, 113.66 mu m +/- 6.88 mu m, and 114.27 mu m +/- 6.90 mu m in measurement zones 1, 2, 3, and 4, respectively. In group 2 (FemtoLASIK), flap corneal thickness values were 115.96mmHg +/- 7.01mmHg, 114.72mmHg +/- 7.17mmHg, 113.54mmHg +/- 6.45mmHg, and 115.30mmHg +/- 6.64mmHg 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.