Keratoconus

An Overview

We see through the cornea, which is the clear outer lens or “windshield” of the eye. Normally, the cornea has a dome shape, like a ball. A cone-shaped cornea causes blurred vision and may cause sensitivity to light and glare. Keratoconus usually affects both eyes, though it often affects one eye more than the other. It generally begins to affect people between the ages of 10 and 25. Sometimes, however, the structure of the cornea is just not strong enough to hold this round shape and the cornea bulges outward and downward like a cone. This condition is called keratoconus.
In the early stages of keratoconus, you might be able to correct vision problems with glasses or soft contact lenses. Later, you may have to be fitted with rigid, gas permeable contact lenses or other types of lenses, such as scleral lenses.

Types of Corneal Cross-Linking

There are two types: epi-off and the experimental epi-on. (“Epi” is short for epithelium, the outer layer of the cornea.)

The epi-off technique means your doctor removes the epithelium before she puts the drops in.

With epi-on, your doctor loosens your epithelium with eyedrops or a sponge before she puts the eyedrops in.

Symptoms of Keratoconus

Signs and symptoms of keratoconus may change as the disease progresses. Conical cornea is another name for the condition. It usually begins in the teen years, and the shape changes in the cornea take place over many years. As the cornea becomes more irregular in shape, it causes progressive near sightedness and irregular astigmatism to develop, creating additional problems with distorted and blurred vision. Increased sensitivity to bright light and glare, which can cause problems with night driving See your eye doctor (ophthalmologist or optometrist) if your eyesight is worsening rapidly, which might be caused by an irregular curvature of the eye Glare and light sensitivity also may occur. They include:

• Blurred or distorted vision
• Increased sensitivity to bright light and glare, which can cause problems with night driving
• Inability to wear contact lenses
• A need for frequent changes in eyeglass prescriptions
• Frequent eyeglass prescription changes
• Sudden worsening or clouding of vision
• Increased nearsightedness or astigmatism
• Glare
• Nearsightedness
• Ring of Discoloration on the Front of the Eye

What Causes Keratoconus?

Tiny fibers of protein in the eye called collagen help hold the cornea in place and keep it from bulging. When these fibers become weak, they cannot hold the shape and the cornea becomes progressively more cone shaped.
Keratoconus is caused by a decrease in protective antioxidants in the cornea. The cornea cells produce damaging by-products, like exhaust from a car.
As the cornea becomes more irregular in shape, it causes progressive nearsightednessand irregular astigmatism to develop, creating additional problems with distorted and blurred vision. Glare and light sensitivity also may occur.
Keratoconus also is associated with overexposure to ultraviolet rays from the sun, excessive eye rubbing a history of poorly fitted contact lenses and chronic eye irritation. In addition, keratoconus is associated with:
An eye injury, i.e., excessive eye rubbing or wearing hard contact lenses for many years.Certain eye diseases, such as retinitis pigmentosa, retinopathy of prematurity and vernal keratoconjunctivitis.

Diagnosed?

Keratoconus changes vision in two ways:

• As the cornea changes from a ball shape to a cone shape, the smooth surface becomes distorted. This is called irregular astigmatism.
• As the front of the cornea expands, vision becomes more near sighted. That is only up close objects can be seen clearly. Anything too far away will look like a blur.
An eye doctor may notice symptoms during an eye exam. You may also mention symptoms that could be caused by keratoconus. These include:
• A sudden change of vision in one eye
• Double vision when looking with just one eye
• Objects both near and far looking distorted

Treatment

In the mildest form of keratoconus, eyeglasses or soft contact lenses may help. But as the disease progresses and the cornea thins and becomes increasingly more irregular in shape, glasses and regular soft contact lens designs no longer provide adequate vision correction.
Treatment for keratoconus depends on the severity of your condition and how quickly the condition is progressing. Mild to moderatekeratoconus can be treated with eyeglasses or contact lenses. For many people, the cornea will become stable after a few years.

• corneal crosslinking. There are two versions of corneal crosslinking: epithelium-off and epithelium-on.
• Glasses and soft contact lenses often cannot provide adequate visual acuity because of irregular astigmatism. Specially designed gas permeable contact lenses are usually the preferred treatment.
• KeraSoft lenses (Bausch + Lomb). These high-water silicone hydrogel lenses can correct up to 20 (D) of nearsightedness or farsightedness and up to -12 D of astigmatism.
• Scleral lenses are the most successful treatment for patients with keratoconus, pellucid marginal degeneration, post corneal transplant, post-refractive surgery complications, irregular corneas and other conditions requiring complex lenses. The major advantage of these highly specialized lenses is the comfort which soft lenses provide and the excellent vision and durability that gas permeable lenses provide.
• Fitting contact lenses on an eye with keratoconus often is challenging and time-consuming. You can expect frequent return visits to your eye care provider so he or she can fine-tune the fit and your prescription, especially if your keratoconus continues to progress.
• Surgery – Corneal transplants have a very high success rate following transplantation, with 98.1% of transplanted corneas surviving the first year, and 97.5% surviving beyond four years. To find out more on corneal transplant procedures.