Measurement of corneal changes after collagen crosslinking using a noninvasive ultrasound system

Abstract

To determine the changes in corneal properties induced by riboflavin-ultraviolet A (UVA) irradiation using a noninvasive ultrasound (US) method in a porcine eye model. Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA. Fresh porcine globes acquired within 24 hours postmortem were divided into equal groups. In the collagen crosslinking (CXL) group, the globes were irradiated with UVA in combination with riboflavin application following the standard protocol. The control group had the same procedures as the CXL group but with no UVA irradiation. Corneal properties were measured before and after treatments in both groups using a quantitative US method. Changes in corneal thickness, density, and stiffness were examined and the difference between the changes in the CXL group and the control group was analyzed. Each group comprised 14 porcine globes. After riboflavin-UVA treatment, there was a significant increase in corneal stiffness (mean 2.59 +/- 0.08 GPa before and 2.70 +/- 0.08 GPa after CXL) (P<.001) and in the speed of sound in corneal tissue (1557 +/- 23 m/s versus 1588 +/- 22 m/s) (P<.001). There was no significant change in corneal stiffness or in the speed of sound in the control group. Corneal thickness increased significantly after the treatment in both groups. No significant change in corneal density was observed in either group. Corneal stiffness increased after riboflavin-UVA CXL, a finding detected using a noninvasive US technique. Dr. Liu has filed a patent application for the general ultrasound technique used in the study. No other author has a financial or proprietary interest in any material or method mentioned.