Astigmatism is not a disease but a common vision condition that causes blurred vision. Most people have some degree of astigmatism. Small amounts of astigmatism do affect vision but may not require treatment. Larger amounts can cause distorted vision, eye discomfort and headaches.
This refractive error occurs when the front surface of the eye (cornea) or the lens inside the eye is slightly irregular or cylindrical in shape. An irregularly shaped cornea or lens prevents light from focusing properly on the retina, resulting in vision being blurred or distorted at all distances.
Astigmatism often occurs with other vision conditions like nearsightedness (myopia) and farsightedness (hyperopia). Collectively, these vision conditions are referred to as refractive errors because they affect how the eyes bend or “refract” light.