1. Relating to a defect in the eye, or in a lens caused by a deviation from spherical curvature, which prevents light rays from meeting at a common focus and so results in distorted images.
2. Suffering from a defect of a lens such that light rays coming from a point do not meet at a focal point so that the image is blurred.
3. A disorder of the vision, usually due to a misshapen cornea, such that light does not focus correctly on the retina causing a blurred image.