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Symptoms and Causes of Keratitis

By: Kathryn Senior PhD - Updated: 28 Oct 2012 | comments*Discuss
Keratitis Eye Infection Cornea Retina

The eye is a complex sensory organ with many different layers and structures. The tough but clear layer on the outer surface of the front of the eye is called the cornea. This acts as a barrier between the eye and the outside world. It prevents dust and debris getting into the eye, it products the eye from infections and it remains clean and clear to allow light in to the retina so that we can see.

For various reasons, injury, illness and infection, the cornea can become sore and inflamed. When this happens, the general condition is known as keratitis but it has a wide range of different causes.

Symptoms of Keratitis

When someone develops keratitis, the classic signs of inflammation are present in the eye – heat, redness, fluid and pain. The eye, instead of looking a bluish white, looks red and blood shot, with prominent tiny veins. The swollen eye will bulge slightly, causing discomfort and pain and profuse tear production and watering is common. The eye and head will feel painful and it can be difficult to tolerate light. Eyesight is affected, because the front of the eye becomes clouded with pus and thick tears, causing haziness and blurring. In very bad cases of keratitis, the pus can become obvious and the eye has a thicker, yellower discharge.

Progression of Untreated Keratitis

If it is not treated and gets worse, keratitis brings a range of more serious complications. The infection can cause a corneal ulcer, where the surface of the cornea becomes broken and rough, with a deep hole reaching into the deeper layers. If a serious bacterial infection is present, a widespread infection of the surface of the eye can lead to many ulcers and this can cause blindness. People in developing countries with trachoma infection often suffer blindness because of untreated infections and trachoma infection is the leading cause of preventable blindness in the world.

What Causes Keratitis?

All types of infectious agent can cause keratitis. Bacterial infections such as staphylococcus or streptococci, which normally live on the skin, can attack the eye if there is an injury or another infection that weakens the immune defences. Fungal eye infections frequently cause keratitis, as do parasitic infestations. Viruses can also infect the eye – common eye infections are caused by Herpes simplex virus, both types 1 and 2, and mumps, German measles and measles can also lead to keratitis.

People who wear contact lenses, particularly the hard contact lenses that need to be kept clean between uses, are prone to infections and often develop keratitis. One of the most common infectious agents involved are tiny amoeba, single celled organisms that can live in the solution used to wet contact lenses before they are placed in the eye.

The most common non-infectious cause of keratitis is sunburn, which occurs in skiers who become snow blind. It can also occur as an occupational hazard in welders; the front of the eye can be burned by the intense heat and light produced by the welding arc. Laser damage can also cause keratitis.

Treating Keratitis

It is obvious that the underlying cause of keratitis must be identified for any treatment to be effective. It is pointless to treat an infectious keratitis caused by a fungal infection, or a keratitis caused by snow blindness with a topical antiviral therapy.

Depending on the cause and severity of the keratitis, it may be possible to treat it with a drug that is contained within eye drops but it is usually necessary to give treatment systemically as well – by a drug that is either taken in the form of tablets, or given by injection.

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