Definition of the pathology

Astigmatism is a visual defect. It causes distortion of the image, both at a distance and at close range. Vertical and horizontal lines are more or less sharp. Astigmatism can be associated with short-sightedness or long-sightedness. It is one of the visual abnormalities caused by refractive errors (deviation of the light beam as it passes through the eye), such as nearsightedness, farsightedness and presbyopia.