Conjunctival intraepithelial neoplasia (CIN) has traditionally been managed with surgical excision, combined with cryotherapy, with a wide range of reported recurrence rates.¹ In cases of CIN that are too extensive to perform a complete surgical excision or in cases in which the surgical margins are involved, ophthalmologists are now using adjunctive topical antineoplastic agents such as mitomycin C^2,3 and interferon α-2b (IFNα-2b)^{4,5,6,7,8,9,10,11,12} in place of, or in combination with, repeat surgical excision. Although the toxicity associated with the topical ophthalmic use of mitomycin C is well recognised,^13–15 IFNα-2b has been reported not to cause ocular surface toxicity.^{4,5,6,7,8,9,10,11,12} We report a case of corneal toxicity, manifest as epithelial microcyst formation, associated with the use of topical IFNα-2b.

Case report

A 64-year-old man with a history of biopsy-proven CIN of the left eye presented to one of the authors (AJA) for evaluation. Twenty-two years earlier, he had undergone a superficial keratectomy and excision of a papillomatous conjunctival lesion from the left eye. Six years before presentation he had undergone a …