Question category: Ophthalmology
A 55 year old female who is on methotrexate for rheumatoid arthritis presents to her GP with a painful red right eye. This came on suddenly and her eye is mildly painful and watering. Her vision has not been affected. On examination there is evidence of redness in the right upper quadrant of the right eye and this is tender. Her pupil is normal as is her conjunctivae. Visual acuity is unchanged and eye movements are normal. Which of the following is the most likely diagnosis?