This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cornea and sclera, Subject name: Ophthalmology
[{'content': 'In the given condition, cause of defective vision is \nSelect and explain. \nA. Astigmatism, B. Hypermetropia, C. Visual axis is obscured, D. Diplopia', 'role': 'user'}, {'content': "Answer: C \nExplanation: Pterygium: - Definition:- A degenerative condition of the subconjunctival tissue which proliferates as vascularised granulation tissue to invade the cornea . Pathogenesis:- * Elastotic degeneration of the subconjunctival tissue with Fibrovascular proliferation . * Destruction of epithelium & Bowman's layer by advancing fibrovascular tissue resulting in corneal scarring. Cause Of Defective Vision In Pterygium:- * Fibrovascular tissue contracts --> flattening of the cornea in the horizontal axis --> ASTIGMATISM {WITH THE RULE ASTIGMATISM } * Obscuring the pupillary region or the Visual axis. Types Of Pterygium:- Depending upon the growth * STOCKER'S LINE:- seen in atrophic pterygium. Iron deposition in front of the head in the corneal epithelium. Ref:- Parson's Diseases of the eye 22nd edition; pg num:- 184", 'role': 'assistant'}]