The Suitability of Experimental Corneal Lesions for Evaluating Local Sulphonamide Therapy.

LONDON mTHE difficulties-in assessing the value of local sulphonamide therapy in infections of-the outer ,eye centre around the absence ,of satisfactory methpds of-inducing such infections in experimental animals. Gonococcal ophthalmia which so readily occurs in man cannot be induced in animals, even when highly virulent organisms are used and the animal is first exposed to various debilitating processes. Much the same' difficulties' arise-with the-other organisms commonly met in the purulent and muco-purulent conjunctivitides. It-is said' (Boros, 1940) that if the reticulo-endothelial system is first blocked by solid particles, such as, those contained in, solutions of Indian ink, infective lesions can,readily , be produced. Such experi'mental lesions are, however, uns,uitable for, pharmacological and. therapeutic studies owing to the severe-u ~, physiological-disturbances-sometimes ending in death-that blocking of the reticulo-endothelial system produces. The' one consistent experimental infection of the outer eye that can be induced in the' intact animal is corneal ulceration produced by inoculation with B.pyocyaneus, but as has been shown elsewhere ($lein and Sorsby,' 1943) such lesions are not. quite suitable for determining the value of local sulphonamide therapy mainly for-the reason that there is considerable doubt as to the value of the sulphonamides in general-in B.pyocyaneus infection. The-work recorded' here is largely an account of attempts to obtain experimental corneal infections suitable for the. study of the value of therapeutic agents in infections of the outer eye. lThege attempts all failed. 1. Experiments with pneumococcus.-Pneumococcus-types 3 and 19 are pathYogenic to the rabbit, but attempts to induce corneal lesions by' direct inoculation into the abraded cornea and by various additional measures were largely negative. Pneumococcus type 19 (Lister Institute strain). Four procedures were tried qut: (a) Direct inoculation to the abraded cornea'of 01 c:c. suspension 3 x ] organisms; suitably exalted by passage into mice: No result in the four eyes thus treated.