A person looking at a cloth with a pattern consisting of vertical and horizontal lines is able to see the vertical lines more distinctly than the horizontal ones. What is this defect due to? How is such a defect of vision corrected?
The person is suffering from Astigmatism. It is a defect caused due to the imperfection in the curvature of cornea. In this defect, a person is able to focus objects with in one direction only and is unable to do so in its perpendicular direction. Astigmatism is corrected with the use of a cylindrical lens.
