Keratoconus is a condition in which the normally aspheric shape of the cornea is distorted and a cone-like bulge develops, resulting in visual impairment. While this is a progressive disease it is generally slow and can stop at any stage from mild to severe. As keratoconus progresses, the cornea bows and thins, becomes irregular and sometimes forms scars.
In very early cases, vision can be corrected with eyeglasses; however, the majority of those with keratoconus require contact lenses to adequately correct vision. In severe cases a corneal transplant may be necessary.
While contact lenses often provide significant improvement in vision, wearing them is not a cure for keratoconus, nor do they alter the course of the disease. Great care and expertise must be used in the fitting of contact lenses for keratoconus. Frequent check-ups and frequent lens changes may be necessary due to subtle and unpredictable changes in the shape of the cornea.
This slide shows a Munson's sign which is a characteristic that some keratoconus patients exhibit. The corneal protrusion pushes out the lower lid when the patient looks down.
A normal topography would show the reflected circles to be round instead of out of round as the pictures below depict.
The rings of light reflected from this cornea are very irregular and distorted resulting in blurry vision. A contact lens is used to make a new surface that is more regular therefore producing better vision.