Astigmatism is a vision condition that causes blurred vision due either to the irregular shape of the cornea, the clear front cover of the eye, or sometimes the curvature of the lens inside the eye. Sometimes, the surface of the cornea is curved more like a football, with both flatter and steeper curves. An irregular shaped cornea or lens prevents light from focusing properly on the retina, the light sensitive surface at the back of the eye. As a result, vision becomes blurred at any distance. When the surface of the cornea has an uneven curvature, vision becomes distorted. This common irregularity, called a "corneal astigmatism," causes blurred or distorted vision because light rays are not focused at one spot to provide clear vision.
Astigmatism is a very common vision condition. Most people have some degree of astigmatism. Slight amounts of astigmatism usually don't affect vision and don't require treatment. However, larger amounts cause distorted or blurred vision, eye discomfort and headaches.
A person who has both a cataract and a corneal astigmatism will not regain high-quality distance vision after surgery to remove the cataract unless the astigmatism is also corrected.