EFFECTS OF AGE ON THE SENSITIVITY OF THE RAT LENS TO HEXANOL IN-VITRO

The Draize eye irritation test involves the injection of 0.1 mi of a t est material into the conjunctival sac of young adult rabbits. A numer ical scale is used to determine if the chemical is an irritating or no nirritating substance. This is the standard eye irritancy test used to day. Aside from ethical concerns, and concerns related to the subjecti vity of the measures, the Draize test fails to acknowledge whether the re is a change in sensitivity of the eye to irritation as the subject ages. Some chemicals, particularly cosmetics and shampoos, are used th roughout a human lifespan. A rat lens model of young (2.5-month) versu s older (16-month) animals was used to show that there is a change in the sensitivity to a known irritant, hexanol, with age, and that recov ery (repair of incurred damage) is also age dependent. The optics of t he in vitro lens, tested using a specially developed Scanning Lens Mon itor, are sensitive enough to show small variations in hexanol damage with various aged lenses. Lenses from 2.5- and 16-month-old rats showe d 100% increases in focal length variability (optical focus), respecti vely, at 0.6 +/- 0.7 and 10.0 +/- 5.3 h after removal from a 2 h expos ure to 100% hexanol. Recovery was seen only with the younger lenses at 46.8 +/- 5.5 h.