Keratoconus

Keratoconus (from Greek: kerato- horn, cornea; and konos cone), the most common form of corneal dystrophy, is a degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than the more normal gradual curve. Keratoconus can cause substantial distortion of vision, with multiple images, streaking and sensitivity to light all often reported by the patient. It is typically diagnosed in the patient's adolescent years. If afflicting both eyes, the deterioration in vision can affect the patient's ability to drive a car or read normal print. Patients with keratoconus are not recommended for Lasik eye surgery.Wikipedia

There are at least eight genetic loci linked to the development of keratoconus, but so far the only genetically well defined one is caused by autosomal dominant mutations in the VSX1 gene on chromosome 20, and associated SNPs can be found through that gene page.