The uvea is the middle layer of the eyeball. It consists of the iris, the ciliary body, and the choroids. The iris is the part of the eye you are looking at when you say a person has blue eyes or brown eyes. Its function is to change the size of the pupil (the round, black looking opening in its center that allows light to enter the eye) by contracting or relaxing muscles that lie within it. The ciliary body is also a muscular structure inside the eye. The choroid is the major supply of blood vessels that bring oxygen and nutrients to the back of the eye.
Uveitis is an inflammation of any of these structures. Iritis is a more specific inflammation of the iris. The two terms are often used interchangeably. We use the word iritis in the following discussion. The inflammation can occur in one or both eyes. Iritis is a serious condition; do not treat it casually or ignore it, hoping it will go away by itself.
Sometimes there are no symptoms at all. Other times, an eye with iritis looks “bloodshot” and may be extremely uncomfortable in bright light. Sunlight or the glare of an automobile headlight at night can even cause pain or aching in the eye or brow. The pain comes from the tightening of inflamed muscles as they constrict the pupil in bright light and the red color comes from the congestion of blood vessels on the outside surface of the eye, which is a reaction too the inflammation. There may also be blurring vision.
What causes iritis?
Although there are many possible causes, most of the time the exact one cannot be identified. Iritis can occur independently or in association with inflammation elsewhere in the body, such as the joints (arthritis or spondylitis) the teeth or sinuses, or the bowels (colitis). Usually, it is not due to an infection. It is not contagious and not related to infectious “pink eye”.
Why is iritis serious?
If iritis is not treated properly there can be complications that threaten the vision. These complications occur because the inflamed iris gets sticky and adheres to the lens of the eye, which lies directly behind it, or to the cornea which is in front of it. The areas of stickiness are called synechiae and can be dangerous because they can block the normal flow of fluid in the eye which can lead to glaucoma. Glaucoma results in very high pressure inside the eye which can lead to blindness. Other complications of iritis include cataracts, retinal swelling, and other internal eye damage.
If the iritis is severe, the intraocular muscles must be rested and the pupil must be kept dilated (enlarged) with cycloplegic eye drops. This help relieve much of the pain because they allow the iris and the other intraocular muscles (the ciliary body) to rest preventing their normal constriction, especially in bright light; the dilation also keeps the iris away from the lens and cornea so that the synechiae and scarring are less likely to form. If synechiae are already present the dilation may pull free those that are not firmly attached. Even though cycloplegic drops blur the vision, which can be annoying and make it difficult to see well enough to read or drive, they are very important and should not be discontinued until you have been told that it is safe to do so.
Other treatment includes steroid eye drops or oral anti-inflammatory agents. If the iritis is severe and does not respond well to medication, you may need steroid injections, given under the conjunctiva (the membrane overlying the eyeball), or steroid pills which must be taken exactly as directed to help reduce serious side effects.
Medications may produce very rapid relief at first, but the complete control of an iritis attack tends to be a slow process. As the inflammation subsides, you will be given instructions for reducing the medications gradually. This is important. Stopping treatment suddenly could result in a flare-up of the attack.
An iritis attack may be completely cleared by treatment and never occur again, or it may recur in the same eye or in the other eye. Once you have had iritis, a red-eye even years later could indicate another attack. If at any time you think an attack may be starting, call for an appointment right away. Be sure to tell any doctor that is treating you that you have a history of iritis.
Self-treatment is not wise. However, if you cannot get the medical help you may begin using the same cycloplegic and steroid eye drops that you used for your last attack. It is generally not a good idea to use this drops that have been in your medicine cabinet for a long time. They may have posted their potency or worse, may have become contaminated with bacteria. Because of the possibility of side effects, you should never take steroid without medical supervision.
American Academy of Ophthalmology
The Eye M.D Association