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Astigmatism is a visual problem in which the cornea of the eye, the outer covering, is misshapen in an irregular way. Instead of being perfectly round, the cornea is slightly football shaped, curving more gently in one orientation (eg, up/down) than in the other (left/right). This causes the focusing point of light - that should fall directly upon the retina at the back of the eye - to sometimes be in front and sometimes be in back of where it should be. In other words, there are multiple focal points, depending on which direction a person is looking, and the vision is therefore blurry. The two eyes may be irregular in different ways from each other as well. The net effect is that visual details are hard to see for both near and far objects and writing.

A less common form of astigmatism is when the lens of the eye, beneath the (normal) cornea, is misshapen. Since the lens is responsible for focusing the light, it stands to reason that an incorrectly shaped lens will lead to poor focus and blurry vision. This form of the condition is called lenticular astigmatism. In either form of astigmatism, a common symptom is headaches after reading, movies, or other situations of increased eye usage.

Like nearsightedness (myopia) and farsightedness (hyperopia), astigmatism is a problem in correctly focusing. These vision problems are therefore not ‘diseases' of the eye in the way that glaucoma or macular degeneration or other progressively worsening conditions are. Nonetheless they can interfere significantly with one's quality of life.

In fact, near- and farsightedness can often be present in addition to astigmatism. In this case, both near and far vision are affected by the astigmatism, but one is better than the other. For example, someone who is nearsighted and astigmatic has unclear vision at all distances, but it is worse for far away objects. The opposite would be the case for a person who was farsighted and astigmatic. Fortunately, these focusing problems can all be detected in standard eye exams and corrected with eyeglasses, contact lenses or laser surgery.

Astigmatism is a common eye problem, found in about a quarter to a third of most populations. It is least common in African Americans, followed by Caucasians. For reasons not understood it is relatively more common in Asian and Hispanic people. It is virtually always present from birth, though it may not be recognized for several years, for example not until a child begins going to school. Toddlers often cannot self-identify a headache, but recurring crankiness after watching TV or movies could be a sign of problems focusing, especially if the child is otherwise well rested and not hungry.

In later life astigmatism can be a side effect of having cataracts removed or other eye surgery. It can occur at any age as the result of scarring during healing of an accidental eye injury. Though not a progressive eye disease, there is no point in ignoring astigmatism since it can be corrected with relative ease and one's life improved.

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