Ex vivo human cornea rigidity after UVA/riboflavin induced cross-linking

Abstract

Objective: The purpose of the current study was to assess changes in human corneal rigidity after treatment with riboflavin and UVA using a new device, the Corneal Displacement Unit (CDU). Design: Experimental study. The CDU was designed to quantitatively measure the effect of cross-linking (CXL) in complete human donor cornea buttons. This apparatus measures the tissue displacement associated to computer-controlled variations in pressure. Methods: Baseline measurements with the CDU were taken from 10 de-epithelialized human corneas. They were exposed to 0.1% riboflavin drops every 2 min for 1 h with exposure to UVA light during the last 30 min after which CDU measurements were taken again. Results were analyzed using a non-parametric test. Significant tests were set at P ≤ .15 and non-significant correlation coefficients at rho ≤ .15 to reject abnormal measurements. For each of the 10 corneas, pachymetry values and 1988 CDU measurements were collected before and after treatment. Results: Pressure measurements averaged across the corneas were similar before and after treatment (P ≥ .99), and were highly correlated (Spearman rho = .88, P < .001). Corneal displacement observations after treatment were significantly different from baseline, showing a reduction of .084 microns on average (P < .001), and thus demonstrating a reduced displacement in cross-linked corneas. Conclusions: The present study demonstrated a significant increase in the mechanical rigidity of human corneas after CXL. The CDU was able to quantify the mechanical strength of whole corneal buttons ex vivo with minimal damage to the tissue.

Keywords

• Collagen cross-linking
• Riboflavin
• Ultra-violet light
• Ex vivo corneal measurements
• Corneal rigidity