What is Uveitis?

What is Uveitis?

Uveitis is a general term describing a group of inflammatory diseases that produces swelling and destroys eye tissues. These diseases can slightly reduce vision or lead to severe vision loss.
The term "Uveitis" is used because the diseases often affect a part of the eye called the uvea. Nevertheless, Uveitis is not limited to the uvea. These diseases also affect the lens, retina, optic nerve, and vitreous, producing reduced vision or blindness.
Uveitis may be caused by problems or diseases occurring in the eye or it can be part of an inflammatory disease affecting other parts of the body.
It can happen at all ages and primarily affects people between 20 – 60 years old.
Uveitis can last for a short (acute) or a long (chronic) time. The severest forms of Uveitis reoccur many times.
Eye care professionals may describe the disease more specifically as:
Anterior Uveitis
Intermediate Uveitis
Posterior Uveitis
PanUveitis Uveitis
Eye care professionals may also describe the disease as infectious or noninfectious Uveitis.

What is the Uvea and What Parts of the Eye are Most Affected by Uveitis?

The uvea is the middle layer of the eye which contains much of the eye's blood vessels (see diagram). This is one way that inflammatory cells can enter the eye. Located between the sclera, the eye's white outer coat, and the inner layer of the eye, called the retina, the uvea consists of the iris, ciliary body, and choroid:
Iris: The colored circle at the front of the eye. It defines eye color, secretes nutrients to keep the lens healthy, and controls the amount of light that enters the eye by adjusting the size of the pupil.
Ciliary Body: It is located between the iris and the choroid. It helps the eye focus by controlling the shape of the lens and it provides nutrients to keep the lens healthy.
Choroid: A thin, spongy network of blood vessels, which primarily provides nutrients to the retina.
Uveitis disrupts vision by primarily causing problems with the lens, retina, optic nerve, and vitreous (see diagram):

Lens: Transparent tissue that allows light into the eye.
Retina: The layer of cells on the back, inside part of the eye that converts light into electrical signals sent to the brain.
Optic Nerve: A bundle of nerve fibers that transmits electrical signals from the retina to the brain.
Vitreous: The fluid filled space inside the eye.

Causes and Risk Factors

What Causes Uveitis?

Uveitis is caused by inflammatory responses inside the eye.
Inflammation is the body's natural response to tissue damage, germs, or toxins. It produces swelling, redness, heat, and destroys tissues as certain white blood cells rush to the affected part of the body to contain or eliminate the insult.
Uveitis may be caused by:

• An attack from the body's own immune system (autoimmunity).
• Infections or tumors occurring within the eye or in other parts of the body.
• Bruises to the eye.
• Toxins that may penetrate the eye.

The disease will cause symptoms, such as decreased vision, pain, light sensitivity, and increased floaters. In many cases the cause is unknown.
Uveitis is usually classified by where it occurs in the eye.

Article republished from: http://www.nei.nih.gov/health/uveitis/uveitis.asp