Keratoconus

What is it?

In keratoconus, the cornea – the clear window at the front of the eye – slowly gets thinner, mostly in its middle and lower part. Instead of keeping its round dome shape, it bulges out into a cone. This makes it hard for the eye to focus, so sight becomes blurred. Both eyes are affected in the end, though one eye often changes first and the two can differ.

It usually starts in the teenage years or the twenties. Figures for how common it is differ: about 1 in 2,000 people in the USA (NEI) and 1 in 500 to 2,000 worldwide (MedlinePlus). It is more common in people who are not of white ethnic background, and in people with allergies such as asthma or eczema.

The cause is not known; genes and things in the environment both seem to play a part. About 1 in 10 people with keratoconus have a parent, brother, sister or child who has it too, but most cases do not run in families.

The first signs

In the very early stages your sight may be normal.

• blurred or cloudy vision;
• short sight (far-away things look blurry) and astigmatism (a focusing problem that blurs and bends what you see);
• sight that keeps getting worse, so your glasses prescription changes often;
• double vision;
• itchy eyes;
• glare and being bothered by bright light.

As it gets worse it may cause eye pain. A few people get hydrops: fluid from inside the eye gets into a very thin cornea and causes a sudden, painful loss of sight, which settles with time.

How doctors find out

A local optometrist (the person who tests your eyes for glasses) can pick up early keratoconus. An eye doctor looks at your eyes with a slit lamp, a microscope with a bright light. NEI says the only way to know for sure if you have a cornea condition like this is a full eye exam with your pupils widened (dilated).

Jelenlegi kezelés

Glasses or contact lenses; sometimes cross-linking

Will it get worse?

Often yes, slowly. How fast it changes and how bad it gets differ from person to person. The cornea usually keeps changing shape from the teenage years until the middle of adult life, and then stops. In advanced cases the cornea can scar, which blurs sight more; MedlinePlus links scarring to long-term contact lens wear or hard eye rubbing on a thin cornea. Moorfields Eye Hospital says keratoconus does not cause blindness.

Glasses and contact lenses help most people

Even in advanced keratoconus, contact lenses can usually correct sight.

• some people can wear soft lenses;
• some wear special hard lenses that change the shape of the cornea.

Cross-linking or a transplant, for some people

Corneal cross-linking can make the cornea stronger. It uses ultraviolet (UV) light to make the cornea stronger.

If contact lenses no longer help, or the cornea is badly scarred, a cornea transplant may be needed: all or part of the cornea is replaced with a donor cornea.

• the operation takes 1 to 2 hours, and most people go home the same day;
• sight improves slowly, over up to 2 years after a full transplant, and glasses or contact lenses are usually still needed;
• you use steroid and antibiotic eye drops every day, and keep using your eye drops long term to lower the risk of the transplant failing;
• the body can reject the new cornea at any time, but if found early this can usually be treated with steroids.

Is there a cure?

Glasses or contact lenses help most people correct their sight, and cross-linking can make the cornea stronger. Research funded by the US National Eye Institute is studying cross-linking, a detailed ultrasound scan to find keratoconus earlier, and how genetic risk factors affect the cells of the cornea.

See the 48 trials you can join

Források

Written in plain words by Frontlight from these pages:

1. Moorfields Eye Hospital (NHS): Keratoconus
2. NEI: Corneal Dystrophies
3. MedlinePlus: Keratoconus (MedlinePlus Genetics)
4. NEI: Research on Corneal Conditions
5. NHS: Cornea transplant