This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Conjunctiva, Subject name: Ophthalmology
Visual impairment in pterygium is due to - 
Select and explain. 
A. Astigmatism, B. Myopia, C. Hypermetropia, D. Hazy cornea
A: Astigmatism
Answer: A: Astigmatism 
Explanation: Visual disturbances occur when it encroaches the pupillary area or due to corneal astigmatism induced due to fibrosis in the regressive stage. Occasionally diplopia may occur due to limitation of ocular movements. ref: A K KHURANA OPHTALMOLOGY,E4, Page-81