Eye Health Center
Eye Health and Keratoconus
We see through the cornea, which is the clear, central part of the front surface of the eye. Normally, the cornea has a dome shape, like a ball. Sometimes, however, the structure of the cornea is just not strong enough to hold this round shape and the cornea bulges outward like a cone. This condition is called keratoconus.
What Causes Keratoconus?
Often the cause of keratoconus is unknown. Some studies have found that keratoconus runs in families, and that it happens more often in people with certain medical problems, including certain allergic conditions. Some think that chronic eye rubbing can cause keratoconus. But most often, there is no eye injury or disease that could explain why the eye starts to change.
Keratoconus usually begins in the teenage years, but it can also start in childhood or up to about age 30. The changes in the shape of the cornea usually occur slowly over several years.
Someone with keratoconus will notice that vision slowly becomes distorted. The change can stop at any time, or it can continue for several years. In most people who have keratoconus, both eyes are eventually affected, although not always to the same extent.
Can Keratoconus Damage Vision?
The changes to the cornea can make it impossible for the eye to focus without eyeglasses or contact lenses. In fact, a corneal transplant may be necessary to regain vision if the condition is severe.
Keratoconus can be dangerous if laser vision correction surgery -- LASIK or PRK -- is performed on the eye.
Anyone with even a small amount of keratoconus should not have laser vision correction surgery.
How Is Keratoconus Diagnosed?
An opthalmologist may notice symptoms during an eye exam, or the patient may mention symptoms, that could be caused by keratoconus. These include:
- Sudden change of vision in just one eye.
- Double vision when looking with just one eye.
- Objects both near and far look distorted.
- Bright lights look like they have halos around them.
Your doctor must measure the curvature of the cornea to be sure you have keratoconus. Several different instruments can be used to do this.
One instrument, called a keratometer, shines a pattern of light onto the cornea. The shape of the reflection of the pattern tells the doctor how the eye is curved. There are also computerized instruments that make three-dimensional "maps" of the cornea, a process called corneal topography.
How Is Keratoconus Treated?
Only a doctor experienced in treating eye problems can recommend the right treatment for someone with keratoconus. Treatment usually starts with new eyeglasses. If eyeglasses don't provide adequate vision, then rigid contact lenses are recommended. Eventually surgery may be necessary.
Keratoconus changes vision in two ways:
- As the cornea changes from a ball shape to a cone shape, the smooth surface also becomes slightly wavy. This is called irregular astigmatism.
- As the front of the cornea expands, the eye becomes more nearsighted. That is, only nearby objects can be seen clearly. Anything too far away will look like a blur.
New eyeglasses can usually make vision clear again in mild cases of keratoconus. Eventually, though, it will probably be necessary to use contact lenses.
WebMD Medical Reference
