Purpose: To assess whether full biomechanical stiffening can be achieved with corneal crosslinking (CXL) when applying a reduced ultraviolet (UV) fluence during the standard irradiation time.
Setting: Laboratory of Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland.
Design: Experimental study.
Methods: Thirty-four freshly enucleated porcine corneas were deepithelialized and soaked with hypoosmolar riboflavin 0.1% solution for 30 minutes. Slow low-irradiance CXL (30 minutes at 1.5 mW/cm2, fluence 2.7 J/cm2) was compared with standard CXL (30 minutes at 3 mW/cm2, fluence 5.4 J/cm2). The controls were soaked with riboflavin but not exposed to UV light. Elastic (stress-strain) and viscoelastic (stress-relaxation) 2-dimensional testing was performed with a commercial stress-strain extensometer to quantify the biomechanical stiffening.
Results: Corneas crosslinked with low and standard UV irradiances had a significantly higher mean elastic modulus (65.9 MPa ± 15.7 [SD] and 67.1 ± 15.6 MPa, respectively) than controls (52.4 ± 12.3 MPa) (P < .001). Also, the remaining stress after 120 seconds of stress-relaxation was significantly higher after CXL with low and standard UV irradiances (159 ± 21 kPa and 158 ± 25 kPa, respectively) compared with controls (135 ± 20 kPa) (P ≤ .013). No difference was observed in low and standard irradiances between CXL conditions (P = .64).
Conclusions: The UV fluence for CXL might be reduced while maintaining the biomechanical efficacy by using a lower UV irradiance and the same irradiation duration. This might open avenues in the treatment of extremely thin corneas.
Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.