Uveitis

Summary

• Uveitis is inflammation of the uvea, one of the layers enclosing the eyeball.
• Uveitis has many different causes, including infection, autoimmune disease and trauma.
• Anterior uveitis, which affects the parts of the uvea at the front of the eye, notably the iris, is the most common type of uveitis.
• Symptoms vary and may be subtle, but can include red, painful eyes and vision problems.
• Depending on the type of uveitis present, treatment may involve antibiotics, antiviral drugs, steroids, immunosuppressants or mydriatics.

Definition

Uveitis is inflammation of a part of the eye called the uvea.

The uvea

The eyeball is enclosed within three layers: the uvea is the layer lying between the outer layer (the sclera) and the inner (the retina, the light-gathering nerve layer). The uvea consists of the iris (coloured structure surrounding the pupil), the ciliary body (located behind the iris, this structure focuses the lens) and the choroid (layer rich in blood vessels that lines the back of the eye and supplies blood to the retina).

Underlying causes and risk factors

The many different causes of uveitis include the following:

• Exogenous uveitis:  caused by external injury to the uvea or invasion of micro-organisms.
• Engodenous uveitis:  1. infection such as a virus (e.g. Herpes) or fungus (e.g. Candida) or a parasite (e.g. Toxoplasmosis) or bacteria (e.g. Tuberculosis).  2. Secondary to a non-infective systemic diseases such as Sarcoidosis. 3. An auto-immune disease such as Rheumatoid Arthritis and Ankylosing Spondylitis or Crohn’s Disease.
• Unknown

Types

Uveitis is classified depending on the structure affected:

• Anterior uveitis: affects the parts of the uvea at the front of the eye, the iris and the ciliary body.
• Iritis: inflammation of the iris
• Iridocyclitis: inflammation of both iris and ciliary body

Anterior uveitis is the most common form of uveitis. As the iris is the structure most usually affected, "anterior uveitis" and "iritis" are often used synonymously. The inflammation is often associated with autoimmune diseases, and a history of these is a risk factor. The disorder may affect only one eye and is most common in young and middle-aged people.

• Intermediate uveitis(or peripheral uveitis): the next most common type. It affects the area immediately behind the ciliary body (pars plana) and the most forward edge of the retina.
• Posterior uveitis: inflammation of the choroid, the part of the uvea at the back of the eye. It may involve the choroid cell layer (choroiditis), the retinal cell layer (retinitis) or both (choroidoretinitis). Posterior uveitis usually follows a systemic infection.
• Diffuse uveitis (or panuveitis): inflammation of all three structures (iris, ciliary body and choroid)

It it persists for more than six weeks the term chronic uveitis is used.

Symptoms and signs

Symptoms and signs of uveitis may be subtle, and vary, depending on the site and severity of the inflammation. Symptoms may include:

• Painfull eye, redness(usually around the cornea)
• Watery eye
• Blurred vision
• Photophobia (sensitivity to light)
• Dark, floating spots ("floaters") in your vision (posterior uveitis)
• Small pupils
• Excessive blinking and squinting
• A normally clear cornea may appear dull or cloudy

Diagnosis

Uveitis is usually diagnosed by ophthalmic examination, consisting of a visual inspection of the internal and external structures of the eye, using  the slit lamp. In more advanced cases, changes may be visible without special instruments. The examination must  also include the measurement of intra-ocular pressure (pressure within the eyeball).

If your doctor diagnoses uveitis and suspects that it is a sign of underlying disease, blood samples may be taken and other tests performed to ascertain the cause.

Treatment

Treatment of uveitis aims to:

• Relieve pain and discomfort.
• Prevent sight loss due to the disease or its complications.
• Treat the cause of the disease where possible.

If the inflammation is caused by an infection, treatment will involve antibiotics or antiviral drugs. Other drugs used to treat uveitis fall into three main groups: steroids, immunosuppressants and mydriatics (pupil dilators).

Steroids

Steroids make up the major part of uveitis treatment. They act as anti-inflammatory and immunosuppressant agents.

The method used to deliver the steroid depends on the severity and location of the inflammation. Different forms used include:

Systemic steroids are mainly used to treat posterior uveitis, but may be considered if anterior uveitis is particularly severe or resistant to treatment with drops or injections.

Follow the instructions for taking steroid tablets conscientiously. The consequences of missing steroid dosages can be severe. Never stop taking steroids or reduce their dosage without your doctor's permission.

Subconjunctival injections is usually given if the eye doesn’t  respond on topicl treatment or if the attack is severe.

Although most people taking systemic steroids only experience a few, if any, significant side-effects, these can be serious and may include epigastric pain, nausea and sleeplessnesss.

Immunosuppressants, usually used in conjunction with steroids, tend to target the immune system more precisely than the latter. However, side-effects of immunosuppressants can be more severe, so careful monitoring is essential. Examples of immunosuppressants: cyclosporin, azathioprine, methohextrate.

Mydriatics

Mydriatic eyedrops, such as atropine and cyclopentolate, are used to treat anterior uveitis by relieving pain and preventing sight-threatening complications. It prevents the iris from sticking to the lens, causing raised intra-ocular pressure.

Mydriatics work by temporarily paralysing the muscles of the iris and the ciliary body (it is the movement of these inflamed muscles that causes pain). When the drops have taken effect, the pupils will be dilated and this may cause temporary blurring of vision.

Outcome

The outcome varies quite considerably from person to person. Uveitis may persist for days to years, but with treatment it can be well controlled. The course of the condition may be characterised by recurrent flare-ups. Early intervention will limit or prevent complications.

Possible complications of uveitis include:

• Raised intra-ocular pressure
• Cataract formation
• Swelling of the macula

Prevention

Timely treatment of known causative disorders may help to prevent uveitis.

When to call the doctor

Call your doctor if you experience any symptoms of uveitis. If these include eye pain or reduced vision, contact your doctor immediately.

If you are taking systemic steroids, consult your doctor if you develop any illness, especially an infection, or if you are concerned about side-effects.

Reviewed by Dr L.C. Boezaart

Reviewed by Dr L.Venter, MB Ch B, MMed (Ophth) + FC Ophth SA , December 2010