the eye
astigmatism
myopia
hyperopia
presbyopia
Astigmatism is an overall inability of the eye to focus clearly at any distance because of uneven curvatures of the cornea. Essentially, the cornea is oval, having a surface shaped more like a football or the back of a spoon rather than being rounded like a baseball. Very frequently associated with myopia, astigmatism can cause light rays to focus at more than one point on the retina, and objects at all distances appear distorted--much the same way as some fun house mirrors make images too tall, wide, thin, or short. Virtually all corneas have at least a tiny degree of astigmatism. For many,, the resulting distortion is not discernible. But as the curvature of the cornea becomes more uneven, image distortion increases. Eyeglasses, hard contact lenses, or toric soft contact lenses are used to correct astigmatism. Astigmatism is often inherited.
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