Uveitis (cont.)

Aside from the redness of the eye(s), the only other visible signs of uveitis are microscopic and can be seen by an ophthalmologist using a slit lamp microscope. Inflammatory white blood cells can be visualized in and around the uvea portion of the eye and in the front portion of the eye under the cornea (the anterior chamber).

The different types of uveitis are classified based on which parts of the uvea are affected: iritis (iris), cyclitis or intermediate uveitis (ciliary body), choroiditis (choroid), or panuveitis (all three parts of the uvea).

Different types are then further classified by cause: autoimmune (when associated with an autoimmune disease in the body), infectious (when caused by a bacteria, virus, fungus, or parasite), traumatic (after trauma to either eye), or idiopathic (no identifiable cause).

Several autoimmune diseases can be associated with uveitis: sarcoidosis, lupus, rheumatoid arthritis, and multiple sclerosis, to name a few. Several infections in the body can also be associated: tuberculosis, Lyme disease, syphilis, herpes zoster (shingles), and others.

An ophthalmologist will ask several questions about the symptoms, both in the eye(s) and the rest of the body (for example, about painful joints, weight changes, skin rashes, etc). The doctor will also need a detailed history of any existing medical conditions and family history of medical disorders.

The vision and eye pressures will be measured, and the examination will involve careful observation of all parts of the eyes.

Though there are several types of uveitis, they all have one thing in common: invasion of white blood cells (immune cells of inflammation found in the bloodstream) from inside the blood vessels of the uvea to outside the blood vessels. These white cells permeate the uveal tissue and also leak out of the uvea into other parts of the eye. This presence of white blood cells is what an ophthalmologist looks for when making the diagnosis. Using a slit lamp, an ophthalmologist can detect white blood cells accumulating in different parts of the eye.

Iritis can present as 'subclinical' with no white blood cells visible, or as subtle microscopic white blood cells floating in the aqueous, the liquid in front of the iris. Sometimes uveitis is not so subtle with large numbers of cells visible and accumulations on the back of the cornea (the clear “dome-shaped” front cover of the eye). These clusters of cells are referred to as 'mutton fat deposits.' In extreme cases, the cells can also form a large pool in the space between the iris and the cornea. This is referred to as a 'hypopyon.'

Cyclitis (intermediate uveitis) presents as white blood cells floating in the clear material just behind the iris (the vitreous) and collections of cells on the surface of uveal tissues behind the iris. Similarly, choroiditis presents as cells in the vitreous and uveal tissue, but further posterior (towards the back of the eye). An ophthalmologist will likely need to dilate the patient's eyes and use special examination techniques to visualize this.

If an associated medical disease is suspected, additional tests or consultation with other specialists may be necessary to identify the condition. These tests might include laboratory evaluation of a small sample of aqueous or vitreous liquid from the eye, blood tests, and/or X-rays. These tests take time. Therefore, usually a treatment plan is initiated based on a clinical judgment before the cause can be definitively identified.

Source: MedicineNet.com
http://www.medicinenet.com/uveitis/article.htm