Ocular Surface Squamous Neoplasia
A. Introduction There have been multiple refinements in the terminology of the epithelial squamous neoplasia until the introduction of the term “Ocular surface squamous neoplasia” (OSSN) by Lee and Hirst in 19951. OSSN is an umbrella term and refers to a spectrum ranging from mild/moderate/severe dysplasia to carcinoma in situ to invasive squamous cell carcinoma involving the conjunctiva and/or cornea2-4. OSSN is the most common tumor of the ocular surface. According to the epidemiological studies, the worldwide incidence of OSSN is 0.02 to 3.5 cases per 100,000 people. Incidence increases with decreasing latitude, being higher in countries located close to the equator. OSSN predominantly occurs in the elderly age group (6th to 7th decade) and in male gender 5-9. B. Etiology and pathogenesis10-27 The presumptive risk factors implicated in the etiology of OSSN include: Excessive exposure to ultraviolet radiation Heavy cigarette smoking Immunosuppressive conditions: Human Immunodeficienc

