Iritis is considered to be a form of uveitis because the iris is a component of the middle layer of the eye called the uvea.

An eye examination helps to discover the cause and lead to proper treatments. There are many less common causes of red eyes.

Some people with the autoimmune disease ankylosing spondylitis (AS) experience episcleritis, though uveitis and iritis are more common eye symptoms. Not everyone with AS experiences eye inflammation.

“It is well known that shingles causes what is known as ‘keratitis’ when it affects the cornea, and ‘iritis’ when it is inside the eye,” Dr. Cohen says. “Both cause pain ...