Iritis is an inflammation of the iris, the part of the eye that makes a person's eye blue, green or brown. It's function is to change the size of the pupil by contracting or relaxing muscles that lie within it.  Iritis can occur in one eye or in both.  It is a serious condition that can lead to blindness.  Most of the time, an eye with iritis looks "bloodshot" and may be extremely uncomfortable in bright light.  Sunlight or the glare of 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 congestion of blood vessels on the outside surface of the eye, which is a reaction to the inflammation.  There are usually some blurred vision too.

Although there are many causes, most of the time the exact one cannot be identified.  Iritis can occur independently or in association with inflammations elsewhere in the body, such as in the joints, teeth, sinuses or bowels (colitis).  Usually it is not due to an infection, is not contagious, and is not related to pink eye.

If iritis is not treated promptly, there can be complications that threaten vision.  These complications occur because the inflamed iris gets "sticky" and adheres to the lens, which lies directly behind it, or to the cornea, which is in front of it.  The area of adhesion can be dangerous because they might block the normal channels for fluid drainage and lead to secondary glaucoma, a serious condition that can lead to blindness.  Other complications of iritis are cataract, retinal swelling, and other internal eye damage.  Therefore, prompt treatment by an ophthalmologist is essential to prevent any blindness.

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 your ophthalmologist right away.  Be sure to tell your doctor that have a history of iritis. If you can't get to your doctor right the way, you may begin to use the same eyedrops you used for your last attack if they have not expired, and schedule an appointment as soon as you can.