Dilated pupil in left eye only

A 32-year-old Caucasian female was referred for a unilateral, dilated pupil. A few hours earlier the patient noted a loss of focusing ability and dilation in the left eye only. Otherwise, the patient, who has a history of migraines, was asymptomatic including a lack of headache at the time of presentation. She did not report previous episodes. Examination was negative for a reverse APD, diplopia, EOM involvement, or ptosis. The BVA was slightly decreased at distance OS (20/25) and near (J2). The remainder of the exam was WNL.

The attached photo shows the pupils at presentation. Given the otherwise normal examination and history of migraines, the patient was diagnosed with benign episodic unilateral mydriasis (BEUM). The patient followed up in 3 days at our office and presented at that time with normal pupils (see the second photo). She reported experiencing a migraine 24 hours after our visit and resolution of the dilation after 48 hours. A brain MRI and MRA were both negative.

Benign episodic unilateral mydriasis is most commonly seen in women with a history of migraines. The dilated pupil is intermittent, lasting for hours to days, and is the only ocular finding. Specifically, no ptosis or EOM involvement is found and the patient may report previous episodes. The dilated pupil will constrict to 1% pilocarpine, in contrast to a pharmacologically dilated pupil. Neuroimaging is not necessarily required if the patient is female, has a history of previous episodes and/or migraines, and the dilated pupil is the only ocular finding.