Man with acute iritis, inflammation of the iris, in his right eye (notice how the pupil is constricted). The iris is the muscular & fibrous curtain which hangs behind the cornea and alters the size of the pupil thereby controlling the amount of light entering the eye. Symptoms of iritis include pain in the eye or forehead and reddening of the margin of the iris. Occasionally dimness of vision may be present. Treatment requires total rest of the eye (dark glasses and atropine drops, which paralyse the muscles of accommodation), accompanied by application of corticosteroids.