Endothelial cell damage after riboflavin-ultraviolet-A treatment in the rabbit

Abstract

Purpose: To evaluate the possible cytotoxic effect of combined riboflavin-ultraviolet-A (UVA) treatment on the corneal endothelium.

Setting: Department of Ophthalmology, Technical University of Dresden, Dresden, Germany.

Methods: The right eyes of 34 New Zealand White rabbits were treated with riboflavin and various endothelial UVA doses ranging from 0.16 to 0.9 J/cm2 (0.09 to 0.5 mW/cm2, 370 nm) and postoperative enucleation times of 4 hours and 24 hours. The endothelial cells were evaluated in histological sections. The terminal deoxynulceotidyl transferase deoxy-UTP-nick-end labeling (TUNEL) technique and transmission electron microscopy were used to detect apoptosis.

Results: There was no endothelial damage in the 6 rabbit eyes enucleated at 4 hours. In those enucleated at 24 hours, there was significant necrosis and apoptosis of endothelial cells in the corneas treated with an endothelial dose of > or =0.65 J/cm2 (0.36 mW/cm2), which is about twice the endothelial UVA dose used in the treatment of keratoconus patients.

Conclusions: In rabbit corneas with a corneal thickness less than 400 microm, the endothelial UVA dose reached a cytotoxic level of > or =0.65 J/cm2 (0.36 mW/cm2) using the standard surface UVA dose of 5.4 J/cm2 (3 mW/cm2). Pachymetry should be routinely performed before riboflavin-UVA treatment; in thinner corneas, irradiation should not be done because of the cytotoxic risk to the endothelium.