Human and rabbit eye responses to chemical insult

Abstract

Groups of eight human volunteers and eight albino rabbits, under controlled laboratory conditions, were exposed in one eye without subsequent rinsing to the same concentrations and volumes of four prototype consumer products: fabric softener, shampoo, hand soap, and laundry detergent. Dose volume was 0.10 or 0.01 ml. The dose concentrations were selected to produce moderate effects with recovery within 24 to 48 hr. Two irritation scales were employed with both human and animal subjects: the Draize scale by a technician and a medical scale used with slit lamp examination by an ophthalmologist. Eyes were examined by both graders before and after dosing at specified intervals until recovery. Mean and maximum irritation scores are presented for each grading time, method, and exposure, as are the mean hours to recovery (clearing) for each exposure. Recovery times for human eyes were consistent with those reported previously for accidental human exposures to similar materials. Correlation coefficients for time to clear, comparing human vs rabbit for each dose volume-species combination across the four test products, were 0.72, 0.1 ml-human vs 0.01 ml-rabbit; 0.66, 0.01 ml-human vs 0.01 ml-rabbit; 0.40, 0.01 ml-human vs 0.1 ml-rabbit; 0.35, 0.1 ml-human vs 0.1 ml-rabbit. Thus, recovery time obtained under conditions of the “Low-Volume” test (0.01 ml-rabbit) better correlates with human eye recovery time (either dose volume) than does recovery time under Draize test conditions (0.10 ml-rabbit). It is concluded that a rabbit eye test based on a 0.01-ml dose volume (low volume test) more accurately predicts human occular response than does the Draize test and should be used to judge new eye irritation methods.