Keratoconus.

Keratoconus is characterized by the presence of corneal distortion (secondary to thinning of the apex) and either Fleischer's ring (found in 57% of patients) or Vogt's striae (found in 44% of patients). Often the only presenting symptom is decreased visual acuity. Steep keratometric readings are not usually diagnostic; 18% of patients with keratoconus have readings flatter than 45.00 D. Treatment requires correction of acuity with spectacles or contact lenses. More advanced cases are generally managed with rigid gas-permeable contact lenses. Corneal scarring occurs in approximately 43% of cases; 10% to 20% of patients require penetrating keratoplasty to restore acuity.