Sometimes the cornea is irregularly shaped, causing the eye to focus an object on two different areas of the retina. This is known as astigmatism. For the cornea to bend light correctly, it should be spherically-shaped, like a basketball. Astigmatic corneas are shaped more like an egg. This causes a distorted view when looking at objects both close-up and far away.
Astigmatism is often associated with myopia or hyperopia, and it usually is present from birth. It may be hereditary, or it may be caused by factors such as pressure on the cornea, incorrect posture, or increased use of the eyes for near activity.
Eyeglasses, contact lenses, or refractive surgery can correct moderate to high degrees of astigmatism. People with low amounts of astigmatism typically wear glasses for driving at night, watching television, or extended near activity.