A Rabbit Model of Corneal Endothelial Injury Induced by Intracameral Injection of 0.05% Benzalkonium Chloride

Abstract

Introduction: Rabbits are currently not suitable to be used as an animal model of corneal endothelial disorders because their corneal endothelial cells (CEC) maintain a highly proliferative capacity in vivo. A recent ex vivo study suggests that intracameral injection (ICI) of 0.1 mL 0.05% benzalkonium chloride (BAC) in rabbits produces a selective endothelial damage. This study was aimed at evaluating the effects of BAC ICI in rabbits in vivo to define the most appropriate BAC dose for inducing a rabbit model of corneal endothelial disease.

Methods: Twenty-four healthy adult New Zealand White rabbits were divided into 4 groups (n = 6) based on the compound injected unilaterally into the anterior chamber: 0.025% BAC, 0.05% BAC, 0.1% BAC, and BSS (Control group). Complete physical and ophthalmic examinations, pachymetry and specular microscopy were performed at 0, 2, 7 and 14 days. After 14 days, rabbits were euthanized and subconjunctival enucleation of the injected eye was performed. Excised corneas were vital-stained and observed under the light microscope to assess the corneal endothelial cells (CEC) morphology and mortality rate. The entire eye globe was sent for histopathology.

Results: Compared to BSS, concentrations of ≥ 0.025% BAC led to significant increases in corneal edema, corneal thickness, mean CEC area and polymegathism. CEC mortality was significantly higher with 0.05% and 0.1% BAC. CEC density and hexagonality were significantly decreased with all BAC concentrations. Higher incidence of conjunctival congestion and corneal ulceration was detected with 0.1% BAC. Histopathology revealed CEC loss and ruled out alterations affecting the rest of the ocular structures.

Conclusion: BAC ICI in vivo leads to dose-dependent corneal endothelial toxicity in rabbits, being 0.05% the minimum required concentration to achieve a sufficient, but not excessive, selective corneal endothelial damage. This method could consequently be used for inducing a rabbit model of corneal endothelial disease.