This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Types of Errors of Refraction, Subject name: Ophthalmology
Cylindrical glass is used for: 
Select and explain. 
A. Presbyopia, B. High myopia, C. Hypermetropia, D. Astigmatism
D: Astigmatism
Answer: D: Astigmatism 
Explanation: Ans. (d) AstigmatismRef: A.K. Khurana 6th ed. 142-43, Harrison's 19th ed./ 195* Astigmatism is a type of refractive error which arises due to irregular curvature of cornea.* Correction of astigmatism is done by using cylindrical lens.