Irregular curvature of the cornea or lens of the eye, distorting the image formed on the retina. A dot is seen as a blob or dash. The most usual condition is regular astigmatism, in which corneal curvature is asymmetrical. Parallel beams of light entering the eye are normally focussed as a point, but are seen by an astigmatic eye as a stripe. This form of astigmatism is corrected by spectacles with a cylin- drical lens.