Ans. is 'a' i.e., Pterygium Pterygium Pterygium is a non-cancerous (non-neoplastic) growth of conjunctiva, characterized by a wing-shaped fold of conjunctiva encroaching upon the cornea from either side within the interpalpebral fissure. Pterygium is always situated in the palpebral apeure. Pathologically Pterygium is a degenerative and hyperplastic condition of conjunctiva. The subconjunctival tissue undergoes elastotic degeneration and proliferates as vascularized granulation tissue under the epithelium, which ultimately encroaches the cornea. The corneal epithelium, Bowman's layer and stroma are destroyed. Etiology & Clinical features Pterygium is more common in people with excess outdoor exposure to sunlight (UV rays), dry heat, high wind and abundance of dust. Therefore it is more common in those who work outdoors. Clinically it presents as a triangular fold of conjunctiva encroaching the cornea in the area of palpebral apeure, usually on the nasal side. Other findings are stocker's line (deposition of iron) Ptergyium is an asymptomatic condition in the early stages, except for cosmetic intolerance. Visual disturbance or corneal astigmatism may occur. Visual disturbances are due to encroachment of pterygium on pupillary area or corneal astigmatism. Occasionally diplopia may occur due to limitation of ocular movements. Treatment Asymptomatic pterygium which is not progressive is best left alone. Surgical excision is the only satisfactory treatment and is indicated for : - 1) Cosmetic reasons, 2) Continued progression threatening to encroach onto the pupillary area (once the pterygium has encroached pupillary area, wait till it crosses on the other side), 3) Diplopia due to interference in ocular movement.