Keratoconus is a disease of the cornea which causes thinning of the central portion of cornea. As this progresses the normal eye pressure causes distortion of the natural round shape of cornea and an irregular cone like bulge develops which causes vision impairment.
The poor quality of vision occurs due to distortion of image caused due to distorted corneal surface. This gives rise to image doubling, ghost images, shadows or flared images.
It does not lead to blindness but it can result in disabling vision in advanced stages.