Light rays entering the eye first cross the clear cornea. Surprisingly, nearly two-thirds of the eye’s focusing power occurs along its front surface (tear film or cornea). The normal cornea should have a semi-spherical contour similar to a baseball. This permits the eye to create a single focused image. If the central cornea is not symmetrical or uniform we say it is “astigmatic.”
Astigmatism, often combined with nearsightedness or farsightedness, occurs when the clear cornea has a non-round curvature – more like a teaspoon or football. Because of that, the eye lacks a single point of focus. People with astigmatism may have a random, inconsistent vision pattern, wherein some objects appear clear and others blurry. The next time you hold some shiny silverware, compare your reflection in a soup spoon to that produced by the teaspoon – that’s astigmatism! Astigmatism is usually present from birth but is sometimes not recognized until later in life. Most astigmatism is fully correctable. Also, it changes very little over time.