Effects of laser in situ keratomileusis (LASIK) on corneal biomechanical measurements with the Corvis ST tonometer

Abstract

Andreas Frings,1,* Stephan J Linke,1,2,* Eva L Bauer,1 Vasyl Druchkiv,1 Toam Katz,1,2 Johannes Steinberg1,2 1Department of Ophthalmology, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany; 2Care Vision Refractive Center, Hamburg, Germany *These authors contributed equally to this work Purpose: This study was initiated to evaluate biomechanical changes using the Corvis ST tonometer (CST) on the cornea after laser in situ keratomileusis (LASIK). Setting: University Medical Center Hamburg-Eppendorf, Germany, and Care Vision Refractive Centers, Germany. Design: Retrospective cohort study. Methods: This retrospective study included 37 eyes of 37 refractive patients. All CST measurements were performed 1 day before surgery and at the 1-month follow-up examination. The LASIK procedure included mechanical flap preparation using a Moria SBKmicrokeratome and an Allegretto excimer laser platform. Results: Statistically significant differences were observed for mean first applanation length, mean first and second deflection lengths, mean first and second deflection amplitudes, radius of curvature, and peak distance. Significant positive correlations were found between the change (∆) of radius of curvature and manifest refraction spherical equivalent (MRSE), ablation depth, and ∆intraocular pressure as well as between AD and ∆HC-time. Each diopter of myopic correction in MRSE resulted in an increase in ∆radius of curvature of 0.2 mm. Conclusion: Several CST parameters were statistically significantly altered by LASIK, thereby indicating that flap creation, ablation, or both, significantly change the ability of the cornea to absorb or dissipate energy. Keywords: LASIK, corneal biomechanics, refractive surgery, Corvis ST