The uvea is the middle layer (tunic) of the eye. It includes the iris, ciliary body, and the blood vessels that serve the retina. Any infection or inflammation of the uveal tunic is called uveitis. The common forms of uveitis are discussed, with emphasis on uveitis as a condition affecting young people more commonly than other eye diseases. Most people with uveitis have pain, so they see a doctor. Physicians look for the other uveitis symptoms as part of any proper eye exam, and with vigilance in high-risk groups. Researchers focused on the underlying conditions that cause uveitis strive to overcome this threat to healthy vision.
What is uveitis?
Uveitis is neither a common vocabulary word nor a common disease. But it is a very important cause of vision loss.
Uveitis is an infection or inflammation inside the eye. And everything inside the eye is important for vision. In its most common form, uveitis of the iris and neighbouring eye tissue, there is usually sharp pain. Enough pain to send a sensible person to an eye doctor. But if uveitis strikes in the middle eye, or even in the inner back layer, damage may not be so evident. In the absence of pain (that is, without any signal that a doctor is needed) any form of untreated uveitis can become a greater threat to vision.
Sadly, uveitis is more common in young people that any other vision-threatening disease. In fact, in juvenile rheumatoid arthritis (JRA), the incidence of the inflammatory type of uveitis can reach upward of one third of sufferers. Physicians recognize this predisposition and counsel their patients to have eye exams at least once every 6 months.
Uveitis can be caused by any of dozens of potential infections, or can appear as a seeming inflammatory response to an infection, but without any evidence of infection or other cause.
When an eye suffers from the trauma of an accident, the resulting inflammation at the front of the eye is, perhaps, the easiest form of uveitis to diagnose because the cause and effect are clear. But in many cases of uveitis, the cause can only be attributed to an immune system response gone haywire.
In medical journals, uveitis has been recognized to be caused by over 100 known pathologies. These include: infection, chronic disorders, trauma and immune system malfunction, as well as chronic conditions affecting other systems of the body, such as diabetes, autoimmune disorders and even rare microbial infections.
Uveitis due to infection can be caused by agents as diverse as spores, protozoa, spirochetes, bacteria and viruses.
JRA uveitis
In juvenile rheumatoid arthritis (JRA), there is an elevated risk that the child's immune system will set off inflammation of the inner front structures of the uvea (the ciliary body and the iris) and affect the inner cornea and lens.
Floaters just one symptom
Having floaters (little lint-like specks that glide through your view) is one symptom sometimes associated with uveitis in the middle and back of the eye. But accurate diagnosis requires a thorough eye examination. Seeing floaters occasionally is so common that it is not a very telling symptom. But since uveitis in the mid and back eye is not necessarily accompanied by pain, any remarkable or unusual experience of seeing floaters warrants an eye examination.
One reason uveitis in the back of the eye is difficult to diagnose and treat is that the uveal layer there, properly called the choroid, is between the retina and the outer eye layer (the sclera), so it is not directly exposed to the view of the eye doctor.
Uveitis in the front of the eye often affects the iris, which is the visible extension of the uvea. Changes in the color or texture of the iris can provide a signal to the doctor of this form of uveitis.
Since the uvea is in such intimate contact with the critical mechanisms of vision, if this layer becomes irritated or inflamed (even if there is no bacteria or virus responsible) the inflammatory condition itself can pose a serious threat to vision. If, however, the condition is detected and treated early, the prognosis for recovery is good. Uveitis in the front of the eye is both more common and more responsive to topical therapy.
The uvea extending to the back of the eye to form the choroid contains most of the arteries and veins that serve the retina. At the front of the eye, in addition to the iris, the uvea forms the ciliary body, source of the liquids which bathe the lens and cornea, bringing them needed nutrients, much like the bloodstream feeds other tissues in the body.
If the eye is injured or a foreign body pierces the outer tissues, the uvea surrounding the injury may become severely irritated and infected, and this could spread if left untreated. Infection elsewhere in the body can also attack the uvea through the circulatory system.
After an eye injury, the eye doctor looks to see if the uvea is involved and will often prescribe antibiotics to help this important tissue fight off infection.
Systemic conditions affecting other parts of the body can be risk factors for uveitis of the front eye chamber. Eye doctors are aware of this, and where risk factors are present, the doctor will want to do a thorough eye exam every 6 months to a year. Such predisposing conditions include juvenile rheumatoid arthritis (JRA), diabetes, and many chronic microbial infections.
In patients with uveitis due to an autoimmune response — that is, without infection but with local inflammation — the goal of treatment is to reduce the immune system’s overactive response in the eye. Often topical steroids are prescribed, but there are many other medications that may be chosen to lower the inflammation depending on the diagnosis and the treatment strategy of the eye doctor. The treatment chosen is discussed with the uveitis sufferer and depends on whether or not the condition has occurred before and how long the uveitis has persisted.
Any time a person experiences poor health, infections, or has a chronic condition that is a risk factor for uveitis, they should see their eye doctor more frequently. Often doctors will refer patients at risk to an eye specialist. If the risk is elevated, the eye doctor will schedule the next appointment for within 6 months, or sooner if any symptoms should arise. The reason is that inflammation associated with uveitis is treatable but, if left untreated, can pose a serious threat to vision.
Advances in early diagnosis, especially in children, are being made. Eye professionals are on the lookout for the symptoms of uveitis. Their success will undoubtedly bring about better prospects for maintaining good vision, in both low- and high-risk groups.
Sources
http://www.uveitis.org/
http://www.nyee.edu/ophthal/uveitis.htm
http://www.adam.com/ency/article/001005.htm
http://www.merck.com/pubs/mmanual/
http://www.immunology.meei.harvard.edu/pxinfo2.htm
http://www.wellweb.com/index/QUVEITIS.HTM
