For the more general class of optical aberrations, see Astigmatism. Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina.This may be due to an irregular or toric curvature of the cornea or lens. The two types of astigmatism are regular and irregular.or the more general class of optical aberrations, see Astigmatism. Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina.