What Cause of "Pink Eye"?

A 43-year-old man presents with left eye irritation that has been present for about 2 weeks. He denies trauma, headache, eye discharge, fever, cough or vomiting, but does have some mild photophobia and slightly blurred vision that doesn’t seem to clear when he blinks. He has had similar symptoms twice in the past 2 years and was told that he had conjunctivitis both times. He took antibiotic drops, which resolved the symptoms after each episode.

Currently, a coworker is taking medication for “pink eye.”

The patient wears soft contact lenses, but denies that he kept them in while sleeping. His past medical history is unremarkable except for hypertension, for which he takes metoprolol. He denies any prior surgeries, including any eye surgeries. There are no rashes.

His vital signs are all normal. His head shows no swelling or temporal artery tenderness. There is no proptosis or eye pain with motion. The lids and lashes appear normal. The right pupil appears normal, but the left pupil is slightly smaller and reacts more slowly. There is also mild bilateral photophobia and consensual photophobia. The right eye is clear, but the left eye shows injection without discharge (Figure).

Look closely at the image. What’s going on?

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