Fig. 3. Optical correction of astigmatism. A. Light from a distant point object is focused at two different positions by the astigmatic eye. The images of the point object are lines. B. The astigmatic eye has two far points, one for each principal meridian. For this myopic eye, the far points are in front of the eye. C. A spectacle lens that corrects astigmatism has two focal points. D. When the focal points of the correcting lens coincide with the far points of the astigmatic eye, the refractive error is corrected.