Some diseases of the cornea (windshield of the eye) lead to an abnormal shape. Since this tissue provides the majority of the focusing power that enables us to see clearly, any change in its shape leads to blurring or distortion of vision. Keratoconus is a heterogeneous disorder in which there is a bulging and conical shape to the cornea. It is caused by numerous factors including gene mutations.
This condition usually begins in young people and is slowly progressive. The cornea assumes a conical shape and gradually thins. It may progress slowly over several years but sometimes stabilizes for a period of time. Often, however, the progression eventually resumes. In some individuals, there is an acute worsening with sudden onset of pain as fluid enters the cornea causing swelling and a marked decrease in vision. This may heal over several months but the cornea may also undergo scarring with permanent loss of vision. Most individuals have no other associated health problems.
The vast majority (90%) of keratoconus occurs sporadically in individuals without a family history of the condition. It can be a part of many systemic conditions and chromosomal disorders such as Down syndrome and individuals with a connective tissue disease. It has also been associated with frequent eye-rubbing, allergies, or sometimes with long-term contact lens wear. However, these associations may only be coincidental and the cause of keratoconus is unknown in most people.
Several genetic mutations have been found in scattered families in which multiple members had keratoconus. Most such familial cases follow an autosomal dominant pattern of inheritance in which affected parents pass the trait directly to their offspring.
The diagnosis is usually made by your eye doctor who has the special equipment to detect the cornea’s abnormal shape. In early cases, appropriately fitted contact lenses restore normal vision. With progression of the disease, this may no longer be effective and some patients eventually need corneal transplants.