Keratoconus

Key points about keratoconus

  • Keratoconus is an inherited eye condition that affects the cornea – the clear tissue covering the front of your eye.
  • The normally round cornea becomes thinned, distorted and irregular affecting your vision.
  • Initial symptoms can be slight blurring or distortion of vision even when wearing glasses or contact lenses. Other symptoms include increased sensitivity to glare and light and distorted vision.
  • Treatment depends on the severity of the condition and ranges from glasses or contacts through to surgery.
Woman outdoors rubbing itchy, sore eyes

The cause is unknown but keratoconus is seen to have a genetic component, which means you inherit it from a parent. 

The cornea is the transparent front surface of the eye. In keratoconus, the cornea becomes thinned, distorted and irregular (cone shaped). This abnormal shape prevents the light entering your eye from being focused correctly on the retina and causes distortion of vision. 

It also has a link to allergic conditions such as atopic eczema and eye rubbing. The condition usually happens in the late teens to early twenties, however, it can be present at any age. It is a progressive disorder and can happen rapidly or take years to develop. It commonly affects both eyes, although sometimes only one eye is affected.

image of a normal eye and cornea compared to an eye with keratoconus

Image credit: 123rf

Symptoms include:

  • nearsightednes
  • astigmatis
  • blurred vision - even when wearing glasses or contact lenses
  • glare at night
  • eye rubbing
  • light sensitivity
  • frequent prescription changes in glasses and contact lenses.

See a doctor immediately if you have any of these symptoms or signs:

  • blurred vision
  • eye pain when seeing lights
  • redness of your eyes
  • nausea or vomiting
  • pain in your eye.

If you are concerned that you might have keratoconus, it is important to see your GP or local optometrist for an eye examination. They will do some initial tests and can help work out what is causing your vision to be blurry.

After these initial tests, you are likely to need more detailed testing by an optometrist and/or an eye surgeon (ophthalmologist). These tests may include the following:

An eye test

You will be asked to read letters from different rows of a chart. This measures how well you see at certain distances.

An examination of the inside of your eye

In this test, drops are put in your eye to make the hole in the centre of your eye (your pupil) wider. This is called dilating your pupils. A special magnifying lens is used to look inside your eye to find out the cause of your blurred vision.

A slit lamp test

In this test, your external eye structures, such as your cornea, eyelids and conjunctiva, are examined using a microscope along with a slit lamp to detect any abnormalities. Before the test, fluorescein drops are put in your eye to make the abnormalities more prominent and obvious. This test checks for eye problems such as keratoconus, injury to the cornea and uveitis.

A corneal topography test

This is a computerised test that creates a map of the curve of your cornea. It is able to detect corneal abnormalities such as swelling or scarring.

A tonometry test

In this test, an instrument is used to measure the pressure inside your eye. This test checks for other eye problems, such as glaucoma.

Treatment of keratoconus depends on its severity. Generally, the management and treatment options for keratoconus can be divided into three categories:

Glasses or contact lenses

In mild cases, vision can be corrected using glasses or contact lenses. There are different types of contact lenses that your eye surgeon or ophthalmologist will be able to recommend to you. A government subsidy may be available to help with the costs of contact lens wear.

Intacs

Intacs are small plastic rings that are inserted into your cornea to improve the shape of your cornea and reduce visual distortion. They can be used alone or in conjunction with glasses or contact lenses.

Surgery

In severe cases when vision does not improve with glasses or contact lenses, surgery may be recommended. The surgery for treatment of keratoconus for many years was a corneal transplant surgery. In recent years, a new treatment called corneal collagen cross-linking is now available. This treatment works by stabilising your cornea and preventing progression. Your eye surgeon or ophthalmologist will be able to recommend the best procedure for you.

Keratoconus(external link) MedlinePlus, US
Keratoconus(external link) Auckland Eye, NZ

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Credits: Healthify editorial team. Healthify is brought to you by Health Navigator Charitable Trust. Content adapted with permission from The Auckland Eye Manual.

Reviewed by: Dr Janine Bycroft, GP, Auckland

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