[f. as prec. + -ISM.] A structural defect in the eye (see quot.), which prevents the rays of light from being brought to a common focus on the retina.
1862. J. Laurence, in Med. Times, 1 Nov., 474/1. Correction both of the astigmatism and the ametropia.
1878. Foster, Phys., III. ii. 411. The cause of astigmatism is … unequal curvature of the cornea.
