Corneal Thickness Changes Following Exposure of New Zealand White Rabbits to Bis [2-(Dimethylamino) Ethyl] Ether Vapor

Abstract

Bis[2-(dimethylamino)ethyl]ether (CAS No. 3033-62-3; DMAEE) is a liquid industrial chemical whose vapor causes glaucopsia, a transient blue-gray haziness of vision, in exposed workers. The possible role of increased corneal thickness as a basis for the visual disturbances was investigated in groups of five female New Zealand White rabbits exposed for 2 h to mean analytically measured concentrations of DMAEE vapor of 0.1, 0.9, 4.6, 8.8,12.2,14.9, 21.1, and 24.8 ppm; a control group was exposed to air alone. Corneal thickness was measured by an ultrasonic pachymeter before and immediately following exposure and at approximately 30 min, 3, 5, 24, 48, and 72 h postexposure, and thereafter as necessary. Eyes were inspected for signs of conjunctival and corneal inflammation and injury at 30 min; 3,24, and 48 h; at 7 days or longer as considered necessary. No conjunctivalirritation or corneal dullness was seen at 0.1 or 0.9 ppm DMAEE vapor, but at 4.6 ppm and above, exposure-related conjunctivitis and corneal dullness occurred with no clear dose-response relationship. Corneal thickness was slightly, although not statistically significantly increased at 4.6 ppm, and not until about 48 h postexposure. At 8.8 ppm and above increases in corneal thickness were measured immediately postexposure and generally in an exposure concentration-related manner, with a maximum at 3 h and slightly increased throughout the evaluation period. Peak increases occurred with 21.1 ppm (23.7% at 3 h). The results accord with DMAEE-induced glaucopsia being the result of transient increased corneal thickness. The no-effects concentration for induced corneal cloudiness was between 0.9 and 4.6 ppm DMAEE vapor, and for objectively assessed increased corneal thickness, between 4.6 and 8.8 ppm.