Eye Doctors

Keratoconus

What is keratoconus?

The cornea is the transparent dome-shaped window on the surface of the eye, overlying the coloured iris. Its smooth round surface is important for maintaining clear vision. In keratoconus the cornea becomes thin and distorted, eventually protruding forwards in a cone-like shape. It typically affects both eyes, but can often be quite asymmetric.

Why does keratoconus develop?

The causes of keratoconus are not very well understood. However there is a genetic tendency, so it can sometimes run in families. There is also an association with allergies and most people with keratoconus have itchy eyes and rub their eyes to some degree. Over several years the pressure on the eye from rubbing may contribute to distortion of the cornea.

Who gets keratoconus?

Keratoconus occurs in young people, often starting in the teens, or even younger. It usually progresses slowly, and then stabilises in the twenties or thirties. It affects males and females in all racial groups, although in New Zealand it is most common in the Māori and Pacific and Indian populations.

What are the main symptoms of keratoconus?

Keratoconus causes blurring and distortion of vision in one or both eyes. It often gets slowly worse over time, but occasionally causes quite a sudden deterioration in vision. People with keratoconus often have associated allergic conjunctivitis, which causes itchy eyes and eye rubbing.

What treatments can help with keratoconus?

There are two main aims in treating keratoconus; improving vision and preventing progression of the disease.

In the early stages of keratoconus, glasses or soft contact lenses may help correct blurred vision. As the cornea becomes more distorted only hard contact lenses are able to improve vision. About 15% of people with keratoconus progress to the stage where corneal transplant surgery is required. Traditionally full thickness corneal transplant surgery has been necessary, but in some cases of keratoconus it is now possible to perform a partial transplant, which has advantages in long term transplant survival. In recent years preventing progression of keratoconus has become a priority for people with mild or moderate keratoconus. Treating allergic eye disease and avoiding eye rubbing may be of some benefit. 

Corneal collagen cross linking (CXL) is a fairly new treatment designed to stabilise the disease. It uses a combination of ultraviolet light and vitamin B2 to stiffen the cornea, slowing or halting keratoconus progression. It is effective in at least 90% of cases and about 50% of people also have some improvement, with better vision and improved contact lens tolerance. CXL may reduce the need for corneal transplant surgery by preventing keratoconus from progressing to more advanced disease. Our corneal surgeon Dr Penny McAllum can advise which treatment is most suitable for you. 

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