Case report A 35 year-old male patient with a history of HIV infection characterized by progressive tumour growth in bulbar conjunctiva of the left eye, corresponding to conjunctival squamous cell carcinoma that responded to treatment with interferon alpha-2a. Discussion Interferon alpha-2b has been used at conjunctival level as a topical immunomodulator treatment, with complete remission of epithelial neoplasms being observed. However, there have not been any previous publications on the use of interferon alpha-2a, which differs from interferon alpha-2b in a single amino acid, for the treatment of conjunctival squamous cell carcinoma.