Keratoconus is a progressive thinning of the cornea. The cornea is the clear front window of the eye, which, along with the intra-ocular lens, focuses light on to the retina. The cornea normally is a smooth, round dome-shaped structure; however in keratoconus it becomes very thin and irregular and it starts to protrude from the centre or below the centre like a cone. This causes blurry vision that is often not completely correctable with glasses.
The disease is multifactorial in origin but there is a strong genetic component which makes it more frequent in certain parts of the world or within certain families.