Herpes simplex keratitis had no specific treatment until 1962, when Kaufman1 found that an antitumoral agent, 5-iodo-2′-deoxyuridine (IDU), was effective against this infection. IDU is an antimetabolite that competes with its analogue, thymidine, in the synthesis of desoxyribonucleic acid (DNA). The cell which has incorporated IDU in lieu of thymidine is unable to reproduce; it is believed that a virus parasitizing that particular cell would use IDU instead of thymidine for its own DNA synthesis. This synthesis would result in a noninfectious virus without capacity for reproduction. It is also possible that IDU acts by blocking the uptake of thymidine by the DNA-synthesizing organism, causing a halt in its reproductive ability.
The efficacy of IDU in the treatment of herpes infections of the cornea has been demonstrated by numerous clinical reports testifying to the complete healing of epithelial ulcers. For this reason, it was believed that IDU did not