A 30-year-old male patient presents with a unilateral red eye and blurred vision in that eye with onset one day ago. The patient is photophobic and has a small pupil in the eye that is red. He denies having any previous episodes. What is going on?

The main ingredients here are recent red-eye, light sensitivity and a small pupil all in the same eye. This sounds very much like anterior uveitis also known as iritis.

Iritis is inflammation of the iris and has several possible causes:

• Eye injury
• Infection from bacteria, viruses, parasites, or fungi
• Inflammatory autoimmune diseases, such as ankylosing spondylitis, lupus, sarcoidosis, and juvenile idiopathic arthritis
• Injury
• Reactions to medicines
• Leukaemia
• Kawasaki syndrome (lymph node disease in young children).

Eye complications can cause permanent loss of vision:

• Abnormal adhesion of the iris to other eye structures (synechiae)
• Cataracts
• Calcium deposits on the cornea (band keratopathy)
• Inflammation of the vitreous
• Inflammation of the retina
• Optic nerve damage in severe cases, causing blindness
• Glaucoma
• Macular oedema.

Recent onset iritis is an ocular emergency and the patient deserves immediate referral to an ophthalmologist.