CBSE Class 10 Answered
why are cylindrical lenses used for the correction of astigmatism ?
Asked by | 09 Feb, 2012, 03:49: PM
Expert Answer
The cornea is the outermost part of the eye. It is a transparent layer that covers the colored part of the eye (iris), pupil, and lens. The cornea bends light and helps to focus it onto the retina where specialized cells (photo receptors) detect light and transmit nerve impulses via the optic nerve to the brain where the image is formed. The cornea is dome shaped. Any incorrect shaping of the cornea results in an incorrect focusing of the light that passes through that part of the cornea.Astigmatism is an image distortion that results from an improperly shaped cornea. Usually the cornea is spherically shaped, like a baseball. However, in astigmatism the cornea is elliptically shaped, more like a football.The lenses are shaped to counteract the shape of the sections of cornea that are causing the difficulty. Hence, only cylindrical lenses are used to correct astigmatism.
Answered by | 09 Feb, 2012, 07:14: PM
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