Astigmatism occurs when the cornea is curved more in one direction than another is. Astigmatism is one of a group of eye conditions known as refractive errors. Refractive errors cause a disturbance in the way that light rays are focused within the eye (and not on the back of the eye). Astigmatism often afflicts people with near-sightedness as well as far-sightedness; this condition might also result due to refractive errors. Astigmatism is not a disease nor does it mean that people with astigmatism have bad eyes. It simply means that they have a variation or disturbance in the shape of their cornea.
Astigmatism usually occurs when the front surface of the eye, i.e., the cornea, has an irregular curvature. Normally, the cornea is smooth and equally curved in all directions and light entering the cornea is focused equally on all planes, or in all directions. In astigmatism, the front surface of the cornea is curved more in one direction than in the other. This abnormality may result in vision that is much like looking into a distorted, wavy mirror. This distortion results because of an inability of the eye to focus light rays to a point. If the cornea surface has a high degree of variation in its curvature, light refraction may be impaired to the degree that corrective lenses are needed to help focus light rays better. At any time, only small proportions of the rays are focused and the remainder is not, so that the image formed is always blurred.
Usually, astigmatism causes blurred vision at all distances. Some people with very high degree of astigmatism may have cornea problem, such as Keratocones. Astigmatism is very common and people are usually born with an irregularly shaped cornea. The exact reason for differences in corneal shape remain unknown. Sometime, astigmatism worsens over time. Astigmatism may cause blurred vision at all distances, distorted images, headache and fatigue, squinting and eye discomfort or irritation. It can also cause the appearance of double-images, particularly at night. Smaller defects related to astigmatism might be ignored. However, if the degree of astigmatism is great enough to cause eyestrain, headache or distortion of vision, then prescription lenses are essential for clear and comfortable vision.
These corrective lenses needed when astigmatism is present are called “Toric Lenses” and have an additional power element called a cylinder. They have greater light-bending power in one axis than in others. Refractive surgery may be able to correct some forms of astigmatism. Proper change of eyeglasses or contact lenses at regular intervals is essential. Astigmatism will not significantly affect the lifestyle at all.