Keratoconus

What is Keratoconus?

We see through the cornea, which is the clear, central part of the front surface of the eye. The cornea usually has a round shape, like a ball.

Sometimes, however, the structure of the cornea is not strong enough to hold this round shape. Over time, the normal round curvature of the surface of the eye can bulge outward like a cone. This condition is called keratoconus.

Keratoconus is usually detected in adolescence or in the 20s, but can also begin in childhood. In some cases, keratoconus is diagnosed at a later age, but usually only when it is mild.

Keratoconus changes vision in two ways:

As the cornea changes from the shape of a ball to the shape of a cone, the smooth surface is also deformed. This change is called irregular astigmatism, which cannot be completely corrected with glasses.
As the front of the cornea becomes sharp, the eye becomes more myopic (poor vision from a distance,onlynearby objects are clearly seen).

What are the symptoms of keratoconus?

The main symptoms of keratoconus are the following:

Vision in one or both eyes gradually deteriorates, usually in late adolescence.
The person may have double vision when looking only with one eye, even with glasses wearing.
Bright lights look like they have halos around them.

Someone with keratoconus will notice that his vision is slowly deformed. This changecan end at any time or can continue for several years. In most people who have keratoconus, both eyes are eventually affected.

How is keratoconus diagnosed?

To establish the diagnosis of keratoconus, the corneal ophthalmologist specialist must measure the curvature of the cornea. For the diagnosis many different tests can be done. The test most often used is called corneal topography.

Corneal topography measures the curvature of the surface of the eye and creates a colored “map” of the cornea. Keratoconus causes very characteristic changes in the appearance of these maps, which allows the doctor to make the diagnosis.

Can keratoconus damage vision?

Keratoconus without treatment can lead to permanent loss of vision. Changes in the cornea make it difficult to focus the eye with or without eyeglasses or typical soft contact lenses.

Keratoconus can be dangerous if laser vision correction surgery such as LASIK is performed on the eye, because it can aggravate the situation. Anyone who has even a small degree of keratoconus should not have laservision correction surgery, unless recommended by his ophthalmologist in very specific cases.

How is keratoconus treated?

There are several methods for treating keratoconus, depending on how serious the condition is. In the early stages of the disease, vision can be corrected with regular glasses or soft contact lenses.

As the keratoconus deteriorates, vision may no longer be able to be corrected with glasses due to irregular astigmatism, and so the patient may need to place a special type of hard contact lens.

For some patients, the disease can proceed to a stage at which they do not have acceptable vision even with glasses or contact lenses. At this point, the doctor may recommend a corneal transplant, which is a surgical procedure to replace the cornea with a cornea by a donor.

Additional treatments

Two additional treatments for keratoconus are implantable ring segments (often referred to as INTACS) and corneal cross-linking:

Implantable ring segments are small devices that are inserted into the cornea to improve vision or facilitate the placement of contact lenses on a patient. In this procedure, which is performed under local anesthesia (the patient’s eye is numb with drops), the doctor creates channels in the cornea and inserts the rings into these channels. Rings help flatten the cornea and partially correct the conical shape caused by keratoconus.
Corneal cross-linking uses ultraviolet light therapy that can slow down or prevent the deterioration of keratoconus. In this procedure, the patient also receives local anesthesia. Drops of a drug containing riboflavin (vitamin B2) enter the eye for up to 30 minutes; then the eye is exposed to ultraviolet light for up to 30 minutes. The corneal crosslinking procedure is designed to strengthen the bonds between the cornea’s collagen fibers and surrounding proteins, which can help keep the cornea from steepening.

Not all patients with keratoconus are candidates for these treatments. Your ophthalmologist can help you decide which, if any, of these treatments can help you.

Does a patient with keratoconus need surgery?

Many patients with keratoconus will never need a corneal transplant. Corneal crosslinking is a significant advance in slowing down or stopping keratoconus, and treatment is important to consider especially in young patients with a sign of keratoconus, so that vision loss can be minimized.

In cases where vision can no longer be corrected with glasses or contact lenses, surgery may be recommended. Patients with keratoconus usually experience improved vision with corneal transplant surgery, although it may take more than a year to stabilize vision and for a patient to benefit from new glasses or contact lenses. Some patients still need special contact lenses after corneal transplantation to have their best eyesight.