This is  a progressive, non-inflammatory condition of the cornea (the front surface of the eye). It is the gradual thinning of the central cornea, which subsequently leads to a developing bulge that looks like a cone. It generally starts around the mid-teenage years to early thirties, and can continue to progress throughout life. There is no known cause, but there are indications that those with affected relatives are more likely to be affected. There has also been an association with excessive eye rubbing.

Keratoconus causes compromised vision. Other symptoms that one may also experience are difficulty with night driving, haloes around lights, headaches or eye strain, frequent change of prescription and light sensitivity.  In its early stages, glasses and soft contact lenses may sufficiently correct vision. In later stages, one may then need to consider using rigid gas permeable lenses instead as glasses and soft contact lenses do not achieve the best visual outcome.