Uveitis is a serious and widespread inflammation of the eye; it can be due to an infection or it can be non-infectious. Uveitis can develop, for example, in people who have inflammatory conditions elsewhere in the body such as some types of rheumatoid arthritis. People who have AIDS are also more prone to severe eye inflammation.
Uveitis: inflammation of the uvea
If you imagine an eyeball in cross section, the uvea is an internal layer that is present in the outer sphere. It is the layer that contains:
- The network of blood vessels that lines the eyeball: this is the choroid.
- The iris, the coloured part of the eye that encloses the pupil.
- The ciliary body, the collection of muscles that control the shape of the lens when we focus our eyes, and the blood vessels that nourish them.
The uvea is a layer that covers the entire sphere of the eyeball, so if it becomes inflamed, this can affect the whole of the eye. This can happen but it is more usual for the uvea to become inflamed in only one part; in the front of the eye, in the middle or at the back of the eye.
What causes uveitis?
There is no single cause and sometimes the initial underlying cause is difficult to identify. People who have had an eye injury sometimes develop uveitis. Someone hit by a cricket ball or squash ball in the eye, for example. Other known causes include:
- An infection: this may get into the eye because of trauma from an accident or injury but the inflammation is due to the infectious agent. Bacteria, viruses, fungi and parasites can all cause uveitis. Specific infections that carry a risk of uveitis include shingles, toxoplasmosis and tuberculosis (TB).
- HIV/AIDS: infection with HIV lowers the ability of the immune system to fight off other infectious agents and can make infectious uveitis more likely.
- An autoimmune disease: in some diseases such as rheumatoid arthritis, psoriasis, inflammatory arthritis of the spine, multiple sclerosis and inflammatory bowel disease, the body mounts an immune response to its own tissues. Antibodies and immune cells can attack the tissues in the uvea causing severe inflammation.
What are the main types of uveitis?
Four main types of uveitis are recognised:
- Anterior uveitis is inflammation in the uvea at the front of the eye only. This affects the iris and the area that surrounds the iris, and sometimes also the ciliary body but it does not impact on tissues beyond.
- Intermediate uveitis describes inflammation of the uvea in the middle of the eye. The ciliary body and the vitreous of the eye, the central part that is filled with a gel-like substance called the vitreous humour, bear the brunt of the tissue damage.
- Posterior uveitis describes inflammation of the uvea at the very back of the eye. This is the layer of blood vessels behind the retina, the retina itself and the optic nerve.
- Panuveitis is the name given to uveitis that affects the anterior, intermediate and posterior uvea. Inflammation is severe and there is a high risk of blurred vision and loss of vision.
Anterior uveitis in detail
This is the most common type in adults and children. It is responsible for about 75 % of cases and can also be called iritis or iridocyclitis.
Anterior uveitis is a type of acute inflammatory condition because it tends to develop without much warning, and then gets better in less than 6 weeks. It causes the white of the eye to look very bloodshot and the affected eye is also sensitive to light and painful. Anterior uveitis associated with trauma and an infection can occur in one eye only. Both eyes are usually affected when the underlying cause is an autoimmune condition.
Intermediate uveitis in detail
This is diagnosed in less than 15 % of cases. It can also be described as vitritis (because the vitreous is involved), pars planitis or cyclitis. Symptoms include seeing ‘floaters’, shapes that seem suspended in front of your eyes. This is due to debris floating in the vitreous fluid. Your vision will also become blurred because of the haze that this creates. Inflammation in intermediate uveitis usually lasts longer than 6 weeks so is described as chronic.
Posterior uveitis in detail
This causes about 20% of all cases and has the greatest potential to lead to loss of sight. The tissues at the back of the eye, the retina and the optic nerve, are inflamed and this can create macular oedema. This is swelling in the macula, the central point in the retina that gives us fine focus. It can also lead to optic nerve damage and degeneration of the peripheral parts of the retina.
This type of uveitis can be caused by infection – the most common infectious cause is toxoplasmosis. Other cases result from autoimmune activity in the eye. Posterior uveitis is very long-lasting, going on for months or years with periods of remission and relapse.
Complications of uveitis
If treatment is not available or someone with uveitis fails to respond to treatment, serious complications can develop:
- Cataracts: these are common in people who have had any type of uveitis. Not only does the inflammation cause increased eye pressure, which increases the risk of cataracts, the steroids used to treat the condition can also make cataracts more likely. Although cataract surgery can solve the problem, the eye must be free of inflammation before it can go ahead.
- A detached retina: this is mainly a complication of panuveitis and posterior uveitis but it is quite rare, affecting only about 5% of cases. Retinal detachment can tear the retina and lead to vision loss.
To prevent these complications and keep uveitis under control in the long term it is important to use treatments as recommended for as long as necessary and to have regular check-ups with your eye specialist.
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