Keratoconus

What is Keratoconus?

Keratoconus occurs in about one out of every 1,000 individuals.  It is one of the more obscure and less widely known eye diseases making it difficult to diagnose.  The disease results in thinning and weakening of the cornea, the clear lens that is the front of your eye.  As a result, the cornea bulges out of its smooth, dome-like structure, and adopts a more conical and irregular configuration.  Because of this change in shape, the cornea loses its ability to form a clear image in the eye and the patient’s vision can decrease drastically.

Why does Keratoconus develop?

In the keratoconic cornea, light is not completely focused because of the corneal distortion.  This causes scattering of light rays and the formation of “visual static”, much like the static that you may find on a TV.  This distortion, and consequent visual static, can increase over time, with decrease in vision. Biologically and structurally, the cornea is made up of layers of collagen protein which are fixed together by natural biologic sugars.  Both the collagen and microstructure of the cornea are abnormal in keratoconus, causing a weakness of the corneal structure which then leads to optical problems.  It is a progressive condition which, aside from distorting the cornea’s natural optics, can also lead to scarring and other problems. The appearance and impact of keratoconus can vary widely from person to person.  In its earliest stages, keratoconus often give the impression of astigmatism or nearsightedness, two of the more common eye conditions.

What causes Keratoconus?

The direct cause of keratoconus is uncertain.  It may have a genetic, inheritable component.  However, in many patients there are no family members with the disease.  Similarly, most children of Keratoconus patients do not develop the disease, but they should be checked in early adolescence for signs.

Keratoconus is characterized by corneal thinning and vision instability.  This may be caused by abnormalities in the normal collagen structure of the cornea.  Collagen is the main structural component of the cornea.  Collagen is a molecule that typically is very strong.  In addition, the cells of the cornea (keratocytes), may not be normal, and contribute to the thinning and instability of the keratoconic cornea.  The linkages of the collagen molecules and lamellae to one another may also be weak in keratoconus.  This may allow the collagen pancakes to slide on one another and exacerbate KC progression.  Because of this, it is important that the keratoconus patient does not rub his/her eyes in order to avoid mechanical shearing of the collagen pancakes.  Finally, Inflammation may also play a role in keratoconus.  Reactive oxygen species, or oxygen free radicals, may damage the corneal cells and collagen structure, and lead to keratoconus progression.  Because of this, avoiding and treating eye inflammation (for instance, eye allergies) also may be important for the patient.