Keratoconus

The cornea is the clear, dome-shaped window at the front of the eye. It helps focus light so that images appear sharp. In keratoconus, the cornea becomes thinner and weaker over time and starts to bulge outwards into an irregular cone shape rather than keeping its smooth, round curve.

This change in shape scatters and distorts the light entering the eye, leading to blurred and warped vision. Keratoconus usually affects both eyes, although often one eye is more affected than the other. It typically begins in the teenage years or early twenties and may slowly progress over a number of years.

Early on, keratoconus often causes mild blurring of vision and increasing short-sightedness or astigmatism, which is a type of distorted vision. People may find their glasses or contact lens prescription needs changing more often than expected. Vision may also become more sensitive to light and glare.

As the condition advances, vision can become more blurred and distorted, and ordinary glasses may no longer give clear sight. Some people notice streaking around lights, double vision in one eye, or halos at night. Rubbing the eyes can make things worse and is best avoided.

The exact cause is not fully understood. It is thought to involve a weakening of the cornea, and a combination of genetic and environmental factors is likely. Keratoconus sometimes runs in families, so having a relative with the condition can increase the risk.

Vigorous, repeated eye rubbing is strongly associated with keratoconus and may speed up its progression, so avoiding eye rubbing is important. The condition is also more common in people with certain allergic eye conditions and some inherited disorders. It is not caused by reading in poor light or by wearing glasses.

Keratoconus is diagnosed by an eye specialist who examines the eyes and measures the shape of the cornea. Because early keratoconus can look like ordinary short-sightedness or astigmatism, special tests are used to detect the subtle changes in corneal shape and thickness.

A key test is corneal topography, which creates a detailed map of the surface of the cornea and can reveal the cone-like bulging even at an early stage. Measurements of corneal thickness are also taken. These tests help confirm the diagnosis and are repeated over time to check whether the condition is progressing.

Treatment depends on how advanced the condition is. In the early stages, vision can often be corrected with glasses or soft contact lenses. As the cornea becomes more irregular, specially designed rigid or other custom contact lenses may be needed to give clearer vision.

To slow or stop the cornea from worsening, a procedure called corneal cross-linking can be used. It strengthens the cornea using special eye drops and ultraviolet light, and works best when keratoconus is caught early while it is still progressing. Other options include small corneal implants to reshape the cornea. In advanced cases where vision cannot be corrected by other means, a corneal transplant may be considered.

Keratoconus cannot be completely prevented, but you can reduce factors that may make it worse. Avoiding vigorous eye rubbing is one of the most important steps, and treating any underlying eye allergies that cause itching can help. Attending eye appointments allows changes to be picked up early.

The outlook is generally good. For many people the condition stabilises over time, and most keep useful vision with glasses, contact lenses or, when needed, procedures such as cross-linking or surgery. Catching keratoconus early gives the best chance of slowing its progression and protecting sight.