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Irregular astigmatism is a type of eye disorder in which the surface of the cornea is marred by peaks, ridges, valleys, and other abnormal shapes. When the cornea is not uniformly smooth, light cannot be collected and focused onto the lens properly. A person with mild irregular astigmatism may have slightly blurry or distorted vision, while a severe case can cause multiple images to appear in each eye that are disorienting and sometimes debilitating. The condition is generally more difficult to treat than other types of astigmatism, but specialized contact lenses and advancements in surgical techniques allow many patients to enjoy at least some relief from their symptoms.
Most people who have astigmatism suffer from the regular variety. In regular astigmatism, the cornea is more or less smooth, but it is on an abnormal curvature. Light enters the lens at a steeper or shallower angle than normal, leading to mild distortions. In the case of irregular astigmatism, there may or may not be an angle problem. Instead, vision disturbances result from irregularities at certain points on the cornea's surface. Bumps and dips refract light in unusual and sometimes unpredictable ways.
The underlying causes of irregular astigmatism are not always easy to determine, and many possible problems may lead to the disorder. Some people have irregular astigmatism from birth due to genetic factors. Others develop problems later in life due to eye injuries or severe infections. In some cases, surgery to correct regular astigmatism or another eye disorder also can lead to accidental damage to the surface of the cornea.
A person who has irregular astigmatism typically has trouble focusing on both close- and far-range objects. The condition is often worse in one eye than the other, and holding one eye closed may help to temporarily see better. If the cornea is seriously malformed, light may be refracted in such a way that the same image appears multiple times on different places on the lens, causing double or triple vision in a single eye. Vision problems can in turn lead to such symptoms as headaches, nausea, and balance issues.
While regular astigmatism can usually be corrected with glasses, contacts, or surgical reshaping, irregular astigmatism typically is less responsive. A type of contact called a rigid gas permeable lens may be helpful in improving a mild problem. The lens, which is curved uniformly, rests on top of the cornea and reduces how much bumps and dents affect incoming light. Delicate laser surgeries may also be performed to attempt to smooth the surface. The results of surgery are not always perfect, but the procedure does help most people see more clearly.