Uveitis: symptoms, causes, diagnosis and treatment

A red eye is not always a simple problem. Uveitis, an inflammation inside the eye, can threaten sight if it is not treated. This guide explains what uveitis is, its symptoms and causes, how it is diagnosed and how it is treated.

What is uveitis?

Uveitis is inflammation of the uvea, the middle layer of the eye. The eye is shaped like a ball, with three layers of tissue around a central, gel-filled cavity:

• the sclera, the outermost layer, the strong white wall that protects the eye
• the uvea, the middle layer between the sclera and the retina
• the retina, the innermost layer, which senses light and sends images to the brain

Why the uvea matters

The uvea contains many blood vessels, the veins and arteries that carry blood to the eye. Because it nourishes important parts of the eye such as the retina, inflammation of the uvea can damage your sight. After the brain, the eye receives the richest blood supply in the body.

Symptoms of uveitis

• sensitivity to light (photophobia)
• blurred vision
• pain
• redness of the eye
• floaters
• reduced vision

Uveitis can come on suddenly with redness and pain, or sometimes as blurred vision without any pain. Left untreated, it can cause blindness.

What looks like a simple "red eye" may in fact be uveitis. If your eye becomes red or painful and does not clear up quickly, have it examined and treated by an ophthalmologist (eye specialist). Never ignore a red eye with reduced vision: it may be the first sign of a sight-threatening disease.

What causes uveitis?

Uveitis has many causes:

• a virus, such as shingles, mumps or herpes
• a fungus, such as histoplasmosis
• a parasite, such as toxoplasmosis
• bacteria, such as syphilis
• a related disease elsewhere in the body, such as arthritis
• an injury to the eye; a severe injury to one eye can even cause inflammation in the other eye (sympathetic uveitis)

In most cases, however, the cause remains unknown. In almost 80% of cases, no cause is found despite a full range of investigations.

How is uveitis diagnosed?

A careful eye examination by an ophthalmologist is extremely important when symptoms appear, because untreated inflammation inside the eye can permanently affect sight or even lead to blindness.

• A thorough slit-lamp examination and a dilated fundus examination (a check of the back of the eye with the pupils widened) are essential in every case.
• An OCT scan, which gives detailed images of the layers of the retina, and FFA (fundus fluorescein angiography) are often done to understand the disease better.
• Your eye doctor may order blood tests, skin tests or X-rays to help make the diagnosis.

Because uveitis can be linked to disease elsewhere in the body, your ophthalmologist will want to know about your general health and may consult your physician or other specialists.

Types of uveitis

Uveitis is named after the part of the eye that is inflamed:

• Iritis (anterior uveitis): inflammation at the front of the eye, in the iris. It usually starts suddenly and may last six to eight weeks; the eye is usually red and painful. It can be linked to conditions such as ankylosing spondylitis.
• Intermediate uveitis: inflammation in the middle of the eye. It can also start suddenly and last for several months; pars planitis is one example.
• Retinitis or choroiditis (posterior uveitis): inflammation at the back of the eye. It starts more slowly and may last longer. The retinal blood vessels may also be inflamed, which is called vasculitis; examples include Eales disease and toxoplasmosis.

How is uveitis treated?

Uveitis is a serious eye condition that can scar the eye and leave permanent visual disability, so it needs treatment as soon as possible.

• Eye drops, especially steroids and drops that dilate the pupil, reduce inflammation and pain.
• Oral medicines or injections may be needed for more severe inflammation. Oral steroids and antimetabolite medicines may be used in very serious cases.
• Steroid injections inside the eye (intravitreal), such as triamcinolone or a dexamethasone implant (Ozurdex), are often given to treat cystoid macular oedema (swelling of the central retina) and inflammation of the vitreous gel.

Complications of uveitis

• glaucoma (raised pressure inside the eye); see glaucoma treatment
• cataract (clouding of the eye's natural lens); see cataract surgery
• neovascularisation (growth of new, abnormal blood vessels), including rubeosis (new vessels on the iris)
• exudative retinal detachment; see retina surgery

These complications may also need treatment with eye drops, conventional surgery or laser surgery. If you have a red eye that does not clear up, see an ophthalmologist urgently.