Background/aims The aim of this study was to evaluate the long-term corneal toxicity of topical chemotherapy with 1% 5-fluorouracil (5-FU) as a sole or adjuvant treatment of ocular surface squamous neoplasia (OSSN).

Methods Forty-one consecutive cases of OSSN were included in this prospective study. Patients underwent topical chemotherapy with 1% 5-FU four times/day for 4 weeks (one course). Adjunctive courses were repeated until clinical and cytological tumour regression. Clinical confocal microscopy was used to check for 5-FU long-term corneal toxicity.

Results Mean follow-up was 89.7±14.4 months (range 63–122 months). Twenty-two patients (53.7%) underwent topical 5-FU as a sole treatment, and 19 patients (46.3%) as adjuvant and/or debulking therapy. The mean number of 5-FU cycles was 1.9 (range 1–5 cycles). Three tumours (7.3%) treated with 5-FU alone recurred during follow-up. Recurrences were successfully treated with additional 5-FU courses. Clinical confocal microscopy showed no long-term difference between the treated eye and fellow (control) eye in: endothelial cells count, pleomorphism and polymegatism, anterior stromal keratocyte density, sub-basal nerve plexus fibre number, density, and beadings and central cornea epithelium thickness (p=NS).

Conclusion Topical 5-FU, as a sole or combined therapy, must be considered a long-term safe and effective treatment for patients affected by OSSN.