Astigmatism

Most of the light coming into the eye is focused by the cornea, the clear covering over the eye’s front. If the cornea is perfectly shaped, then light is focused to a fine point. If the cornea is not perfect (that is, if it is more curved in one direction than another), the focus point is stretched out. This causes blurred vision, and the condition is known as astigmatism.

If the notion of the cornea’s curves is hard to visualize, think of it like this. If the cornea is curved equally in every direction, it is like a slice off of a baseball. If the cornea is not equally curved, it is more like a slice off of a football. Another way to think of it is the back of a spoon, which is more steeply curved in one direction and less in the other.

Astigmatism may exist alone, or it may be combined with myopia (nearsightedness) or hyperopia (farsightedness). Astigmatism is corrected with special lenses called cylinders. While that may sound odd, cylinder is simply ground into the lenses when the glasses are made. Contact lenses can often be used, and refractive surgery can also correct it in many cases.