Distortion of the corneal curvature that causes optical distortion. Usually due to focal thinning, biomechanical weakness, excess eye rubbing, genetic factors, or combinations of these causes. Absent treatment, keratoconus can be progressive, such that it can cause progressive visual compromise. Mild to moderate keratoconus can be treated with specially-fit contact lenses. In the past, significant to advanced keratoconus was only treatable by corneal transplant surgery. In the current era, a strengthening treatment called UV Corneal Cross-Linking or CXL can stabilize affected tissue, preventing further progression; though this treatment cannot restore the cornea to a non-distorted state. A combination of CXL and specially-fit contact lenses (custom-fit RGP, hybrid lenses, or scleral RGPs) can often restore excellent vision.
