Corneal Biomechanics Following Epi-LASIK

PURPOSE: To evaluate corneal biomechanical changes following epi-LASIK. METHODS: In this prospective study of 51 patients, corneal hysteresis (CH), corneal resistance factor (CRF), and intraocular pressure (IOP) were assessed using the Ocular Response Analyzer (ORA, Reichert Technologies) preoperatively and at 1, 3, 6, and 12 months after epi-LASIK. Repeated measures analysis of variance (ANOVA) was used to compare changes over time (alpha=.05). Intraocular pressure was also measured by Goldmann applanation tonometry. RESULTS: Corneal hysteresis decreased from 10.22±1.65 mmHg preoperatively to 8.17±1.25 mmHg at 1 month, 8.46±1.44 mmHg at 3 months, 8.63±1.31 mmHg at 6 months, and 8.53±1.49 mmHg at 12 months. Corneal resistance factor decreased from 10.01±1.80 mmHg preoperatively to 7.82±1.68, 8.03±1.85, 7.77±1.50, and 7.80±1.66 mmHg at 1, 3, 6, and 12 months, respectively. Repeated measures ANOVA showed a significant change over time for both CH and CRF (P<.0005). All measures of IOP changed significantly over time (P<.0005). CONCLUSIONS: Epi-LASIK resulted in a significant change in CH and CRF postoperatively. Although some recovery occurred over time, CH, CRF, and IOP did not revert to preoperative levels.