Can you shed some light on this patient's blurred vision?

Morgan, a 38-year-old office worker, presents with a new dilated left pupil.

She reports that, in the past 24 hours, vision in her left eye has become blurred when reading, but distance vision has been unaffected.

Today, there has been associated modest left ocular pain with mild photophobia.

She feels otherwise well, with no associated headache, visual blurring or neurological or other systemic symptoms.

She is generally well, has no past medical history of note and takes no regular medications. There has been no recent or remote eye trauma.

Examination

Morgan’s vital signs are within normal limits. Her Glasgow Coma Score is 15, and she appears well. Her visual acuity is 6/5 uncorrected bilaterally for distance.

Near vision is informally assessed. Morgan has difficulty making out near print with the left eye, but her right near vision is intact.

Pupil