Bilateral streptococcal corneoscleritis complicating beta irradiation induced scleral necrosis.

Comment 5-FU is an antimetabolite which interferes with normal cell mitosis. It interfers with the S phase and the G2 phase of the cell cycle which correspond, respectively, with the synthesis of DNA and cellular components required for mitosis.' As corneal epithelial cells are constantly undergoing replication they are particularly susceptible to its toxic effects. Reduction of dosage has been suggested as a method of reducing complications including potential toxicity to corneal epithelium.7 However in this case minimal dosage resulted in toxicity to the cornea. Diabetes mellitus is associated with impaired healing of corneal epithelium owing to the increased thickness of the basal lamina resulting in impaired organisation of epithelial cells and anchorage to underlying stromal collagen.910 This case demonstrates that in patients with compromised corneas even judicious use of very small doses of 5-FU may result in serious corneal complications. We feel that band keratopathy is a contraindication to subconjunctival injections of 5-FU and the possible delay in healing of epithelial defects in patients with diabetes means that in such cases it should be used with extreme caution and stopped immediately if epithelial defects appear.