(See also Introduction to Corneal Disorders.)
The condition usually begins between the ages of 10 and 25. Both eyes are always affected, causing major changes in vision and requiring frequent changes in prescription for eyeglasses or contact lenses in many people. The cause is unknown, but people are more likely to develop keratoconus if they have any of the following:
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Another family member who has keratoconus
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A tendency to develop many allergies (sometimes called atopy)
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A tendency to vigorously rub their eyes
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Lax eyelids
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Certain connective tissue disorders (for example, Ehlers-Danlos syndrome, Marfan syndrome, and osteogenesis imperfecta)
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Disorders that are apparent at birth and cause poor vision (for example, Leber congenital amaurosis, retinopathy of prematurity, and lack of an iris in the eye)
Treatment
Contact lenses often correct the vision problems better than eyeglasses. There are many designs of contact lenses (for example, rigid gas permeable, hybrid, scleral) that may be well tolerated and give good vision. But, sometimes the change in corneal shape is so severe that any contact lenses either cannot be worn or cannot correct vision.
Ultraviolet light treatments that stiffen the cornea (called collagen cross-linking) are useful in early keratoconus to prevent further progression.
The insertion of corneal ring segments (objects that change the shape of the cornea to help correct refraction) seems to improve vision by allowing people to better tolerate wearing contact lenses. Corneal ring segments prevent certain people from needing corneal transplantation.
In severe cases, corneal transplantation may be needed to restore vision.
