Keratoconus

What is keratoconus?

We see through our cornea, the clear bit of the front surface of the eye. It is normally round, shaped like a ball. Sometimes, the cornea's structure weakens and is no longer strong enough to stay in this rounded shape. Over time, the eye's surface bulges out, and its shape becomes more like a cone.

Keratoconus can change our vision in two ways:

• When the cornea changes shape, it can also cause the eye's surface to warp. This is referred to as an irregular astigmatism, a condition that can't be corrected completely by wearing glasses
• When the cornea steepens, it causes more nearsighted (nearby objects are clear, but vision at a distance is poor). This means that new glasses are needed more frequently

What are the symptoms of keratoconus?

The main symptoms of keratoconus are:

• Bright lights appear to have rings or halos around them
• Double vision may be experienced when using just one eye (even when wearing glasses)
• Vision becomes gradually worse, in one or both eyes

Patients notice that their vision becomes distorted slowly, a change that can end at any time or continue for years. Both eyes are usually affected. Keratoconus is usually detected in people in their late teens or 20's. It can also begin in childhood, when it appears at a more rapid rate, or later in life, when it is usually mild.

What causes keratoconus?

The exact cause of keratoconus is unknown, and there are no eye diseases or injuries that explain why the changes begin to occur. Some research has shown that keratoconus might run in families and occurs more often in people with certain medical conditions. People with keratoconus often rub their eyes more, which may speed up the development of the condition.

How is keratoconus diagnosed?

To diagnose keratoconus, a doctor must first measure the curvature of the cornea. Several diagnostic tests can confirm a diagnosis, with the test used most often being topography. This measures the curvature of the eye's surface and gives a colored map of the cornea. In patients with keratoconus, there are very distinctive changes in these maps, which confirm a diagnosis.

Can keratoconus damage vision?

Keratoconus can cause permanent vision loss if it is not treated. The changes to the cornea's shape make it difficult for the eye to focus, even with the help of glasses. Corrective laser vision surgery can also be dangerous for anyone with any degree of keratoconus, as it can make the condition worse.

How is keratoconus treated?

Treatment for keratoconus will depend on how severe the condition is. If it is in the earliest stages, glasses or soft contact lenses can correct vision. As keratoconus develops, and the irregular astigmatism worsens, glasses may not work, and a hard contact lens may need to be fitted.

Some patients may be candidates for treatments called implantable ring segments or corneal crosslinking:

• Implantable ring segments, or INTACS, are small rings inserted into the cornea to make it easier to fit contact lenses, or to improve vision. Under local anesthesia, a doctor makes channels in the cornea within which the tiny rings are inserted. The rings can partly correct the cornea's cone shape by flattening it
• Corneal crosslinking can slow down or stop keratoconus. Under local anesthesia, droplets of a medicine with riboflavin (vitamin B2) are put in the eye for 30 minutes, followed by exposure to ultraviolet light for a further 30 minutes. This helps strengthen bonds between the collagen fibers in the cornea and surrounding proteins and prevents it from changing shape

In very severe cases, a cornea transplant may be recommended, in which a patient's cornea is replaced with one from a donor.

Does keratoconus require surgery?

Procedures such as INTACS and corneal cross-linking are very effective at slowing down or stopping keratoconus, especially in younger patients. These advances can minimize vision loss and many patients will never need a transplant. In severe cases, or for people who aren't candidates for these procedures, corneal transplants offer improved vision, and glasses or special lenses may still be required to provide the best vision possible.