Keratoconus
Keratoconus is a non-inflammatory, progressive ectasia of the cornea. It is characterized by progressive thinning and steepening
of the central cornea into a cone-like shape. As the cornea steepens and thins, the patient experiences a decrease in vision,
which can be mild or severe depending on the degree to which corneal tissue is affected.
Onset of keratoconus occurs during the teenage years-mean age of onset is age 16 years-but onset has been reported to occur
at ages as young as 6 years. Keratoconus rarely develops after age 30. Keratoconus shows no gender predilection and is
bilateral in over 90% of cases. In general, the disease develops asymmetrically: diagnosis of the disease in the second
eye lags about five years after diagnosis in the first. The disease process is active for about five to 10 years, and
then it may be stable for many years. During the active stage, change may be rapid.
Typically, vision loss can be corrected early by glasses or soft contact lenses; later, due to the abnormal shape of
the cornea and the onset of increased myopia and irregular astigmatism, rigid (hard) contact lenses are required for
optical correction and functional vision. Contact lenses provide a uniform refracting surface to improve the patient’s
vision, while at the same time they work to support the bulging cornea. Contact lenses can improve vision, but be
uncomfortable to wear for extended periods – sometimes beyond just a few hours a day. Further, they are believed to
contribute and exacerbate corneal scarring, which may be a manifestation of the disease. Patients typically are
informed upon diagnosis that they would likely require contact lenses eventually. Although most patients can continue
to read and drive, some feel quality of life is adversely affected. Patients undergo eye examinations annually or
more frequently to monitor progression. About 20% of patients will eventually need a corneal transplant.
Keratoconus has no known cure, and many people do not even know they have it because it begins as nearsightedness
(myopia) and astigmatism. It is a progressive disorder that may advance rapidly or sometimes take years to develop.
It can severely affect the way we see the world, including simple tasks such as driving, watching TV, or just
reading a book. Some keratoconus patients have described their vision as being “blind with light”.
Various types of surgery are available for the patient with keratoconus who has progressed beyond correction
with rigid contact lenses. Penetrating keratoplasty is the most common. In this procedure, the keratoconic cornea
is prepared by removing the central area of the cornea, and a full-thickness corneal button is sutured in its place.
An alternative is lamellar keratoplasty, a partial corneal transplant; it should be noted that this alternative is
used in less than 5% of cases.
Intrastromal Corneal Ring Segments (INTACS) have been in use for more than three years in the U.S. as a surgical
treatment of keratoconus. Implants are inserted to help reshape the cornea to its original, natural shape, thereby normalizing
the cornea’s architecture and adjusting for the myopia and irregular astigmatism caused by keratoconus.
(Adapted from material copyrighted by INTACS, Addition Technology, Inc.)
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