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 you 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.