Keratoconus is a rare eye condition in which the normally round, dome-like cornea (the clear front window of the eye) becomes thin and develops a cone-like bulge.  The changes may stabilise over a few months or continue for more than 20 years. Usually Keratoconus is diagnosed in the teens or twenties however it affects approximately 1 in 2,000 people in the UK.

In February 2013 I was diagnosed with Keratoconus after noticing a significant change in my eye sight over a short period of time. Luckily the condition had been caught before it became aggressive and I was offered Collagen Cross Linking treatment (custom-made riboflavin drops saturate the cornea, which is then activated by ultraviolet light) which I had done in March 2013. Collagen Cross Linking is not a cure for Keratoconus but the aim of this treatment is to stop the progression of the condition.

http://keratoconusgb.com/2012/11/19/blogs-about-keratoconus-for-you-to-read/