What is keratoconus?
We see through the cornea, which is the clear, central part of
the front surface of the eye. The cornea normally has a round shape, like a
ball. Sometimes, however, the structure of the cornea is just not strong enough
to hold this round shape. The normal pressure inside the eye makes the cornea
bulge outward like a cone, and this condition is called keratoconus.
Why do people get 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 conditions. But most often, there is no eye injury
or disease that explains 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
occur slowly, usually 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.
Can keratoconus damage vision?
Keratoconus does not make people go blind. However, the changes
to the cornea will make it impossible for the eye to focus without eyeglasses or
contact lenses. Keratoconus can be dangerous if laser vision correction surgery
– LASIK or PRK – is performed on the eye because it can worsen the condition.
Anyone with even a small amount of keratoconus should not have laser vision
correction surgery, unless they know that things could get worse and decide with
their surgeon that it would be their best option.
How does the doctor know whether someone has keratoconus?
The doctor may notice some things during the examination, or the
patient may mention symptoms, that could be caused by keratoconus. These are:
- Sudden change of vision in just one eye
- Double vision when looking with just one eye
- Objects both near and far look distorted, but not blurred. In other
words, small details of the objects are clear, but the shapes or colors look
wrong. Later, distant objects do become blurred.
- Bright lights look like they have halos around them.
These things might be related to keratoconus, but your doctor
must measure the curvature of the cornea to make sure. Several different
instruments can be used to measure the curvature of the cornea. None of them
actually touch the eye.
One instrument, called a keratometer, shines a pattern of light
on 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 an eye doctor can recommend the right treatment for someone
with keratoconus. Treatment usually starts with new eyeglasses, and then contact
lenses are recommended. These will correct the vision problems caused by
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. The resultant change in the eye glasses
measurement 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. Rigid lenses are used most frequently in keratoconus patients.
Is there any way to correct keratoconus surgically?
For most people with keratoconus, the only treatment needed is
the correct prescription for eyeglasses or contact lenses. A small number of
cases of keratoconus keep getting worse, however, and, eventually, contact
lenses cannot give clear vision. In other cases, the keratoconus or the use of
contact lenses over the years will have side effects. These side effects can
make the cornea cloudy. When these things happen, corneal transplantation might