The uveal tract may become inflamed because of infection, injury, a bodywide autoimmune disorder (which causes the body to attack its own tissues), or for unknown reasons.
Symptoms may include eye ache, eye redness, floaters, loss of vision, or a combination.
Treatment typically includes corticosteroids (as eye drops, taken by mouth, or injected into or around the eye), drops that dilate and relax the pupil in the affected eye, and sometimes drugs that suppress the immune system.
The uveal tract consists of three structures:
The iris, the colored ring around the black pupil, opens and closes to let more or less light into the eye, just like the shutter in a camera.
The ciliary body is the set of muscles that, by contracting, allows the lens to become thicker so the eye can focus on nearby objects. By relaxing, the ciliary body allows the lens to become thinner so the eye can focus on distant objects. This process is called accommodation.
The choroid, which lines part of the back part of the eyeball, extends from the edge of the ciliary muscles to the optic nerve at the back of the eye. The choroid lies between the retina on the inside and the sclera on the outside. The choroid contains both pigmented cells and blood vessels that nourish the inside parts of the eye, particularly the retina.
Part or all of the uveal tract may become inflamed. Inflammation limited to part of the uveal tract is named according to its location:
Anterior uveitis is inflammation in the front of the uveal tract, including the iris.
Intermediate uveitis is inflammation in the middle of the uveal tract, and typically also involves the jellylike substance that fills the eyeball (called the vitreous humor).
Posterior uveitis is inflammation in the back of the uveal tract and can involve the retina and choroid.
Panuveitis is inflammation that affects the entire uveal tract.
Sometimes uveitis is referred to by the name of the specific part that is inflamed. For example, iritis is inflammation of the iris, choroiditis is inflammation of the choroid, and chorioretinitis is inflammation that involves both the choroid and the overlying retina. Inflammation of the uveal tract is limited to one eye in many people with uveitis but may involve both eyes.
The inflammation has many possible causes. Some causes are limited to the eye itself, and others are disorders that affect the entire body. In most people, no cause is identified, and they are said to have idiopathic uveitis (or uveitis of unknown cause).
Many people with uveitis have a disorder that also affects organs elsewhere in the body. These include inflammatory diseases, such as Behçet syndrome, ankylosing spondylitis, juvenile idiopathic arthritis, sarcoidosis, reactive arthritis, inflammatory bowel diseases (Crohn disease and ulcerative colitis), and, among Asians and some Hispanics, Vogt-Koyanagi-Harada disease. Some people have widespread infections, such as tuberculosis, syphilis, or Lyme disease.
Other possible causes include infections that may affect only the eye, such as herpes (caused by herpes simplex virus) infection, shingles (caused by varicella-zoster virus), toxoplasmosis, and cytomegalovirus. Cytomegalovirus occurs mainly in people with compromised immune systems, such as those infected with human immunodeficiency virus (HIV) or who take drugs that suppress the immune system.
Eye injuries are a common cause of anterior uveitis.
Although rare, some drugs (such as pamidronate, rifabutin, sulfonamide antibiotics, and cidofovir) can cause uveitis.
The early symptoms of uveitis may be mild or severe, depending on which part of the uveal tract is affected and the amount of inflammation.
Anterior uveitis typically has the most troublesome symptoms. Severe ache in the eye, redness of the conjunctiva, pain with exposure to bright light, and a slight decrease in vision are typical. A doctor may be able to see prominent blood vessels on the surface of the eye near the edge of the cornea, white blood cells floating in the fluid that fills the front part of the eye (aqueous humor), and deposits of white blood cells on the inside surface of the cornea.
Intermediate uveitis is typically painless. Vision may be decreased, and the person may see irregular floating black spots (floaters).
Posterior uveitis typically causes decreased vision and floaters. The optic nerve may become inflamed (see Optic Neuritis). Symptoms of this inflammation include loss of vision, which may vary from a small blind spot to total blindness.
Panuveitis may cause any combination of these symptoms.
Uveitis can rapidly damage the eye. It can cause long-term, vision-threatening complications, such as swelling of the macula, damage to the retina, glaucoma, and cataracts. Many people have only one episode of uveitis. Others have periodic recurrences over months to years or chronic inflammation requiring long-term therapy.
A doctor bases the diagnosis on the symptoms and a physical examination. During the examination, the doctor uses a slit lamp. A slit lamp is an instrument that enables the doctor to examine the eye under high magnification. If the doctor suspects a disorder that also affects other organs, appropriate tests are done.
Uveitis treatment must start early to prevent permanent damage. Treatment almost always includes corticosteroids, usually given as eye drops. Corticosteroids can also be taken by mouth or injected into or around the eye. Drugs to dilate the pupils, such as homatropine or cyclopentolate drops, are also used.
Other drugs may be used to treat specific causes of uveitis. For example, if infection is the cause, drugs may be given to eliminate the infecting organism.
Occasionally, other treatments are necessary, such as surgery, use of a laser, or drugs taken by mouth or injected by vein (intravenously) that suppress the immune system (immunosuppressants).