Question

An eye defect in which one cannot distinguish between vertical and horizontal lines is called.
A). Myopia
B). Astigmatism
C). Trachoma
D). Glaucoma

Answer 1

Hint A vertical line is any line parallel to the vertical direction. A horizontal line is any line normal to a vertical line. Horizontal lines and Vertical lines do not cross each other.

Complete step by step answer:
Astigmatism is an imperfection in the curvature of your cornea-the clear, round dome covering the eye's iris and pupil- or in the shape of the eye's lens. Normally, the cornea and lens are smooth and curved equally in all directions, helping to focus light rays sharply onto the retina at the back of your eye.
Astigmatism is caused by an irregular curvature of the eye's cornea or lens. If your cornea or lens isn't evenly curved, light rays aren't refracted properly. With astigmatism you have blurred or distorted vision at near and far distances.
Astigmatism is a type of refractive error caused when either your cornea or lens has mismatched curves. This makes your vision blurry because there are two image points.
Astigmatism is often present at birth and may occur in combination with nearsightedness or farsightedness. Often it's not pronounced enough to require corrective action. When it is, your treatment options are corrective lenses or surgery.
Symptoms
-Blurred or distorted vision
-Eyestrain or discomfort
-Headaches
-Difficulty with night vision
-Squinting

Hence: option B is correct.

Note: Astigmatism is diagnosed by an eye exam. A complete eye exam involves a series of tests to check your eye health and a refraction, which determines how your eyes bend light. Your eye doctor may use various instruments, aim bright lights directly at your eyes and ask you to look through several lenses.