<prompt> Astigmatism is due to-Irregularity of curvature of corneaIrregularity of curvature of lensForward displacement of the lensIrregularity of curvature of cornea Irregularity of curvature of lens  <response>: Ans. dRef: Khurana optics 2e, p. 79; Parsons 22e, p. 52Most common cause of astigmatism is abnormalities of curvature of cornea. It is usually congenitalLenticular astigmatism is rare, seen in lenticonus cone shaped lens, congenital tilling, oblique placement, traumatic subluxation of lens 