Ocular irritancy responses to various pHs of acids and bases with and without irrigation

Acids and alkalies were instilled into the eyes of 2 groups of rabbits; the eyes of one group were washed with tap water 30 s after exposure. Damage seen in washed and unwashed eyes was not always related to pH. Some strong acids with greater acidity than pH 2.5 produced opacities while 0.3% hydrochloric acid with a pH of 1.28 produced no ocular damage. Phenol (5%) and acetic acid (5%) with pHs greater than 2.5 produced damage equivalent to or greater than that produced by equal concentrations (w/v) of the mineral acids. All alkalies with pHs ranging from 11.5 to 13.5 produced opacities and other ocular damage of different degrees depending upon the alkali and its concentration. For example, low concentrations of some alkalies in the pH range from 11.3 to 12.8 produced no ocular changes. The duration of the corneal opacities produced by phenol, 1% sodium hydroxide, acetic acid and anhydrous sodium carbonate and the onset of corneal opacity produced by 5% sulfuric acid, the weak acids and 1% sodium hydroxide were reduced as a result of washing the test eyes 30 s after instillation of the test material. These data suggest that acidity and alkalinity of the test material are not the only factors to be considered in relation to a substances' capacity to produce severe ocular injury. The concentration of the test chemical and its period of contact with the eye prior to washing are also important.