Ocular Surface Squamous Neoplasia

Ocular surface squamous neoplasia (OSSN) is a term used for precancerous and cancerous epithelial lesions of the conjunctiva and cornea. It is more common in countries with high exposure to solar ultraviolet radiation. The two other major etiological factors in the development of OSSN are human papillomavirus and AIDS. The OSSN lesions arise commonly within the interpalpebral fissure, mostly at the limbus. It may be difficult to differentiate clinically between conjunctival intraepithelial neoplasia (CIN) and invasive squamous cell carcinoma. Despite modern imaging techniques, the definite diagnosis is made by incisional or excisional biopsy. Surgical excision of OSSN is the traditional method of treatment. Adjuvant cryotherapy and brachytherapy have been used to reduce the recurrence rate. Since the 1990s, topical medical therapy has been used extensively as the sole treatment or as an adjuvant to surgical excision. Topical drops of mitomycin C, 5-fluorouracil, and interferon α2b have shown promising results, lowering the recurrence rate significantly. Intraocular invasion and metastasis of conjunctival squamous cell carcinoma are rare.