Question

Astigmatism for a human eye can be removed by using an additional:
A. concave lens
B. convex lens
C. cylindrical lens
D. prismatic lens

Answer 1

Hint:There are three options to correct astigmatism, by glasses, contact lenses or laser eye surgery. There are also other types of defects in eye i.e, myopia, hypermetropia and presbyopia and to remove these, we have to use different types of lenses.

Complete Step by Step Answer:
In above three options, when we use lenses to remove astigmatism then the cylindrical lens has been used for a human eye. An eye which cannot focus on both horizontal and vertical lines simultaneously is suffering from defects called astigmatism for such an eye horizontal part of the object will not be visible clearly as the vertical part. This arises when the corner of the eye has different curvature in different directions. This can be corrected by using glasses with the cylindrical lens.

Additional Information:
Astigmatism is an imperfection in the curvature of the eye into the cornea or in the lens of the eye. Astigmatism is a common vision problem caused by an error in the shape of the cornea of the eye with astigmatism, the lens or cornea of the eye which is into the front surface of the eye, has an irregular curve. This can change the way light passes or reflects through the retina. This causes blurry, fuzzy or distorted vision.

Note:You can get confused between concave and convex lens i.e, for which defect we have to use these lenses. Convex lens used for hypermetropic eye while concave lens used for myopic eye.