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Many patients with myopia have some degree of astigmatism, or ovalness to their corneae. It is the most common refractive condition, and occurs to some extent in most eyes. Astigmatism occurs when the cornea is shaped more like a football/rugby ball than a basketball. As a result, patients with astigmatism experience distortion or tilting of images because of unequal bending of light rays entering the eye. Patients with high degrees of astigmatism have blurred vision not only for distant objects, as with myopia, but for near objects as well.
Astigmatism is also measured in diopters. Of all myopic people, 50% or more have astigmatism as well. Most of these people have corrections of less than 1 diopter. The table below shows the categories of severity for astigmatism:
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