Astigmatism is a refractive condition in which the shape of the cornea (front surface of the eye) is not the same all the way around, like a football. A normal cornea is the same circular shape all the way around, like a basketball. The shape of the cornea is one of the most important aspects of determining the nature of a patient's prescription. The other cause of astigmatism is the alignment of the crystalline lens, which is located behind the iris (colored part of the eye). The main symptom of astigmatism is blurred vision. Because the cornea is not shaped properly, when light is being focused by a cornea with astigmatism the two different curves project two separated images on the retina. The more astigmatism that is present, the further apart the images appear which promotes blurred, sometimes doubled vision.
The cause of astigmatism can be congenital, which means the patient is born with it. Heredity is thought to be an attributing factor and it is common to see multiple members of the same immediate family with similar amounts of astigmatism. It can be located in children and adults. It can sometimes be normal when the patient is young and develop over time. Eye injuries or surgeries can also cause the condition to develop. It can be corrected with several different methods. The most common way of correcting it is with spectacle lenses in your eye glasses. The lenses of the glasses has the exact power needed to make the two different focuses of light from the two different curves of the patient's cornea to focus on the retina in the same exact position, providing a clear, sharp image. Another common method is with contact lenses.
There are contact lenses that are able to correct the two different curvatures of the cornea and focus the two beams of light at the same point. Usually eyeglasses give the patient a clearer image because the blinking of the eyelids moves contact lenses with each blink. Also the power in the contact lenses is usually higher or lower than the actual power needed. Refractive surgery is another method used to physically change the curve of the cornea so that the whole cornea has the same curvature. A yearly eye examination is needed to diagnose and properly treat this condition as the level of power needed to correct it will change as time passes.