Advanced surface ablation with a new software for the reduction of ablation irregularities

PURPOSE: To study the differences in early corneal cellular events and biomechanical properties after femtosecond laserassisted LASIK performed using conventional or inverted sidecut angles. METHODS: In the laboratory study, left eyes of 24 rabbits underwent LASIK flap creation with a 70° or 115° sidecut. The contralateral eyes served as controls. The corneas were harvested 24 hours postoperatively. In the clinical study, 2 eyes of each patient (n = 29) were randomized to corneal flap creation with 70° or 115° sidecut angles during LASIK. The Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Depew, NY) was used to assess biomechanical properties of the cornea. RESULTS: In rabbit eyes, epithelial ingrowth was observed more frequently in flaps with 70° side cuts compared to flaps with 115° sidecuts. Corneas with 70° sidecuts showed significantly increased apoptotic cells compared to 115° sidecuts in the central (P = .001) and peripheral (P = .004) regions. Fiftyeight eyes of 29 patients were included in the clinical study. An overall reduction in Goldmanncorrelated intraocular pressure, cornealcompensated intraocular pressure, corneal resistance factor, corneal hysteresis measurements, p1 area, p2 area, and p1 area 1 and p2 area 1 was noted 37 ± 2 months after surgery (P < .001). No significant difference was observed in the change of any of these parameters between both groups (P = .146). CONCLUSIONS: Significant differences in wound healing were observed in rabbit corneas that underwent LASIK with conventional or inverted sidecuts. Variation in flap sidecut angles did not alter the longterm biomechanical properties measured with the ORA in patients after LASIK.