Neutral red release from pre-loaded cells as an in vitro approach to testing for eye irritancy potential

Many potential alternatives to the Draize eye irritation test are general cytotoxicity tests, which require modification if they are to become relevant components of an acceptable battery of tests. Preliminary studies were made on the exposure of fibroblast-like cells, pre-loaded with a vital dye (neutral red), to high concentrations of test materials for brief periods. Measurement of loss of neutral red from damaged cells provides a readily quantifiable endpoint. When the results obtained with eight detergent formulations were compared with maximum Draize eye scores, a better correlation was obtained with conjunctival and iris effects than with corneal scores or average Draize scores.