This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Degenerative Conditions, Subject name: Ophthalmology
[{'content': 'Most common cause of low vision in pterygium? \nSelect and explain. \nA. Astigmatism, B. Retinal Detachment, C. Corneal ulcer and perforation, D. Myopia', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Astigmatism Etiology & Clinical features in Pterygium -o 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 outdoorso Clinically it presents as a triangular fold of conjunctiva encroaching the cornea in the area of palpebral aperture, usually on the nasal side. Other findings are Stocker's line (deposition of iron)o Ptergyium is an asymptomatic condition in the early stages, except for cosmetic intoleranceo 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.", 'role': 'assistant'}]