Carbachol HCl-Induced Opacity of Porcine Isolated Cornea

Abstract

The in vitro development of porcine corneal opacity induced by carbachol was monitored using a simple, specially constructed opacitometer. Corneas were used intact, without epithelium, or without endothelium, or stroma only. Solutions of carbachol were applied to both surfaces, to the epithelial surface only or to the endothelial surface only. When carbachol was applied either to both surfaces or to the epithelial surface only, there was a significant increase in opacity compared with controls in the order: both epithelium and endothelium removed>epithelium removed>endothelium removed>intact. However, when applied to the endothelial surface only of intact and endothelium-removed corneas, carbachol caused an opacity comparable to control values. This confirms that the drug is safe for use as a topical application in the eye. However, the opacity which develops in corneas in response to benzalkonium chloride indicates that great care must be taken in determining the optimal concentration to use as a “wetting agent”.