Penicillin-streptomycin-gelatine discs in the treatment of hypopyon ulcers.

MULES (1894) wrote that "where the action of micro-organisms on an abraded surface may cause or is causing destructive changes, the indication would be to remove the irritating element and allow the natural process of repair to heal the breach of surface". Thus the best results are likely to be achieved by that mode of administration which will give the maximum concentration of the drug in the anterior segment of the eye, especially the cornea. Since the advent of the sulphonamides and antibiotics, attempts have been made to treat corneal ulcers by parenteral, subconjunctival, and topical administration of these drugs. Penicillin is active against Grampositive, and streptomycin mainly against Gram-negative organisms. The combination of these two antibiotics has a wide range of activity and has been commonly used in the treatment of corneal ulcers. Streptomycin, being fat-insoluble, penetrates the permeable membranes with difficulty and its passage from plasma to aqueous is very poor. With systemic administration the concentration of streptomycin in the ocular tissues is very low (Leopold, 1950). The level of penicillin in the aqueous humour after massive systemic administration is distinctly lower than that obtained by subconjunctival injection or even by the use of penicillin ointment (Sorsby, 1948). The cornea has the added disadvantage that its nutrition is especially poor in the central part, where most of the ulcers occur. Penicillin and streptomycin administered systemically are, therefore, ineffective in the treatment of corneal ulcers, except in so far as they control the inflammation of the tissues around the eyeball. Subconjunctival injections of the antibiotics give a suitable concentration in the eye for combating the intra-ocular infections and rapid improvement can be achieved in this way (Bignell, 1951; Clark and Locatcher-Khorazo, 1951; Sorsby and others, 1952). Penicillin (Sorsby and Ungar, 1948) and streptomycin (Sorsby, Ungar, and Bailey, 1952) are suitable for subconjunctival injection as they are readily soluble in water and only slightly irritant. Penicillin and streptomycin penetrate the intact corneal epithelium with difficulty if administered as drops or ointment. When the epithelium is