Changes in ocular biomechanics after femtosecond laser creation of a laser in situ keratomileusis flap

Abstract

Purpose: To evaluate ocular biomechanical parameters with the Corvis ST, a noncontact tonometer combined with an ultra-high-speed Scheimpflug camera, before and after creation of a femtosecond laser-created laser in situ keratomileusis (LASIK) flap.

Setting: Private practice, Siena, Italy.

Design: Prospective consecutive study.

Methods: Right eyes of patients having LASIK were assessed with the dynamic Scheimpflug camera before and after femtosecond laser (LDV Z4) flap creation but before mechanical flap lifting.

Results: Twenty-eight eyes of 28 patients were evaluated. Before flap creation, the mean values on the dynamic Scheimpflug camera were intraocular pressure (IOP), 15.04 mm Hg ± 3.99 (SD); central pachymetry, 550.8 ± 101.0 μm; applanation 1 length, 1.721 ± 0.134 mm; applanation 2 length, 1.674 ± 0.287 mm; applanation 1 velocity, 0.126 ± 0.031 m/s; and deflection amplitude, 1.039 ± 0.141 mm. After flap creation, the mean values were IOP, 16.10 ± 3.11 mm Hg (95% confidence interval [CI], 0.44-1.78; P < .05); central pachymetry, 561.8 ± 35.9 μm (95% CI, -28.9 to 50.9; P = .21); applanation 1 length, 1.789 ± 0.1492 mm (95% CI, 0.003-0.134; P < .05); applanation 2 length, 1.759 ± 0.259 mm (95% CI, -0.005 to 0.173; P = .08); applanation 1 velocity, 0.136 ± 0.022 m/s (95% CI, 0.001-0.017; P < .05); and deflection amplitude, 1.029 ± 0.151 mm (95% CI: -0.043 to 0.025; P = .34).

Conclusion: The dynamic Scheimpflug camera showed changes in biomechanical properties after femtosecond creation of a LASIK flap as indicated by an increased applanation 1 length and applanation 1 velocity.

Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned.