A condition in which the cornea of the eye is asymmetrically curved, causing out-of-focus vision. The image does not focus on the retina in a sharp point. The cause of astigmatism is unknown. It is usually present from birth, and often occurs together with nearsightedness or farsightedness. A minor degree of astigmatism is considered normal and does not require correction. Astigmatism is very common.

Difficulty in seeing fine detail at both distance and near.

Astigmatism is easily diagnosed by a standard ophthalmic exam with refraction test. Special test are not usually required. Children or others who cannot respond to questions can have their refractive error measured by a test using reflected light called retinoscopy.