Common refractive error of vision that results from an irregularly shaped CORNEA. Astigmatism may affect one EYE or both eyes. Typically the irregularity results in two focal points of light that reach the RETINA instead of a single focal point, resulting in blurred or distorted images. Astigmatism often coexists with HYPEROPIA (farsightedness) or MYOPIA (nearsightedness) and tends to run in families.
Corrective measures include eyeglasses, contact lenses, and REFRACTIVE SURGERY. Mild astigmatism may not produce noticeable vision disturbances, in which case it does not require correction. The success of corrective measures depends on the extent and nature of the corneal irregularities. Astigmatism often accompanies age-related changes in the eyes and vision, and is a common SIDE EFFECT of CORNEAL TRANSPLANTATION.
Less commonly astigmatism results from irregularities in the surface of LENS, called lenticular astigmatism. Options to correct for lenticular astigmatism are CORRECTIVE LENSES or lens-replacement surgery to implant an intraocular lens.