astigmatism - A condition in which the front surface of the cornea does not conform to the normal “spherical” curve, although the eye is perfectly healthy. Because the cornea is unevenly curved, it refracts (bends) the light rays that strike it to differing degrees.
The lens is then unable to bring all the rays into focus on the light-sensitive retina. A minor degree of astigmatism is normal and does not require correction.
More severe astigmatism causes blurring of lines at a particular angle and requires correction, which be achieved by special “cylindrical” glasses that can be framed at a precise angle, contact lenses that can give an even spherical surface for focusing, or laser surgery.
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