Corneal Endothelial Toxicity Secondary to Topical 5-fluorouracil

5-fluorouracil (5-FU) is an important chemotherapy adjunct for the management of conjunctival and corneal dysplasia. Since it is possible for this agent to gain access to the anterior chamber, several reports in the literature have demonstrated 5-FU long-term safety and efficacy. Although recent publications reported that topical 5-FU has no cytotoxic effect on the corneal endothelium, we report a patient affected by bilateral ocular surface squamous neoplasia who has developed significant endothelial density and morphology changes after starting a course of 5-FU.