Contributor: Gordon K. Klintworth
Astigmatism is an unequal curvature of refractive surfaces of the the eye that cause light to not be sharply focused on the retina, but to become spread over a diffuse are. Astigmatism is common and is usually caused by a defective curvature of the cornea. Forty four percent of human eyes have >0.5 diopters (D) of astigmatism and in 8% the astigmatism is 1.5 D. Astigmatism can be a manifestation of high myopia [myopia - high] [astigmatism - high myopic]. Astigmatism can be a complication of as several corneal diseases as well as of methods used to treat them, such as a keratoplasty or LASIK. Methods of treating astigmatism include PARK and LASIK.