An 80-year-old woman with possible iritis

Case scenario

An 80-year-old woman presents feeling ‘off colour’. She is noted to have a red right eye. On questioning she reports decreased vision over four days, but no pain. Only the right eye has reduced vision: the patient can count only fingers. She has bilateral cataracts and, in her right eye, a cloudy cornea and circumlimbal injection. I suspect acute iritis and send her to an ophthalmologist.

In the absence of pain, can acute glaucoma be excluded? How common is acute iritis? What initial treatment should the patient have and is referral needed for this? Is investigation for underlying causes required?