Astigmatism is an optical defect in which vision is blurred due to the inability of the eye to focus one point on the retina. This happens due to the irregular curvature of the cornea or lens.
A perfect lens or cornea has the shape of a ball with the same radius in every direction. A toric lens has the shape of an egg with different radius´. Each radius refracts the light different. The eye is not focusing in one focal point it is focusing in two lines.
Astigmatism arising from either the cornea or crystalline lens can be corrected by a toric lens such glasses or contact lens.
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