Uveitis is a general term which refers to inflammation of the eye. It encompasses a wide variety of disorders. Since the uvea has a rich supply of blood vessels, it tends to be the focus of inflammatory reactions within the eye. This inflammation can damage sight by a variety of mechanisms. Uveitis is thought to account for about 10% of all blindness in the United States.
What is the uvea?
The uvea, which is commonly called the uveal tract, is a collection of structures in the middle layer of the eye. These structures include:
• The choroid: this is the middle blood vessel layer of the eye wall, between the sclera and retina
• The iris: this is the coloured structure in the front of the eye that regulates the amount of light entering the eye
• The ciliary body: this is a muscular ring at the base of the iris that changes the shape of the lens to help us focus and produces the fluid (aqueous) that normally fills the eye
Diagram showing the various structures in the eye that make up the uvea.
What is inflammation?
Inflammation is the first response of the immune system to tissue damage. The response tends to be a collection of fluid, protein, and inflammatory cells that makes the tissue swollen, red, warm and sometimes painful. If inflammation is severe enough, it can cause the tissue to not function properly. The inflammation is our immune system’s attempt to limit the damage and bring about a healing process.
Why does inflammation of the uvea damage vision?
The eye is a complex and delicate structure. Inflammation can have negative effects on the various parts of the eye and affects its function. Some of these damaging effects include: corneal scarring, cataract formation, glaucoma, blood vessel disruption, and retinal damage.
What causes uveitis?
There are many different causes of uveitis; these may range from conditions affecting only the eye to conditions that affect the entire body. The following is a list of the most common causes of uveitis:
• Infection: infection from a virus, fungus or parasite can trigger the body’s immune system to mount a response against the tissue in the eye
• Injury to the eye
• Autoimmune disease: an autoimmune disease is a condition in which the body’s immune system incorrectly recognizes a tissue in the body as “foreign” and mounts an immune response against that tissue (this can lead to inflammation). Examples of autoimmune diseases include rheumatoid arthritis and scleroderma.
• Others: there are dozens of other causes for uveitis; many of these are disease that affect the whole body
• Unknown cause: (this is called idiopathic; frequently, the cause for uveitis in a patient is not determined)
What are symptoms of uveitis?
Symptoms of uveitis are different according to where in the uvea the inflammation is. Symptoms that can occur with uveitis include:
• Eye pain • Redness in the eye • Light sensitivity • Blurred vision • Floaters
What are the different types of uveitis?
You may recall that the uvea is a group of tissues in the eye; it includes the choroid, iris and ciliary body. There are 5 types of uveitis, characterized by where in the uvea the inflammation is:
• Iritis: iritis occurs in the front part of the uvea, the iris. This is the most common form of uveitis, and usually does not last for a long period of time.
• Cyclitis: cyclitis occurs when the ciliary body (the muscles controlling the shape of the lens) become inflamed; this form of uveitis usually lasts a few months.
•Pars Planitis: pars planitis refers to inflammation involving a portion of the ciliary body between the ciliary muscle and the retina. This is the most common cause of posterior uveitis in children, and when it occurs in adults, is sometimes associated with multiple sclerosis.
• Choroiditis: posterior uveitis is inflammation of the choroid, the middle layer of the eye wall. Choroiditis is slower to develop than the other forms of uveitis, but it can last for months or even years.
• Pan-uveitis: pan-uveitis occurs when inflammation occurs in all parts of the uvea.
DIAGRAM COMING SOON
How is uveitis treated?
It is important that uveitis be treated as soon as possible to prevent further damage to the eye. If the inflammation is not severe, eye drops that decrease the inflammation and dilate the pupil usually decrease the inflammation and pain. However, sometimes the inflammation from the disease is so severe that oral anti-inflammatory or immunosuppressive medications, and injections into or around the eye may be required.
