I’ve been told by a hospital-based eye specialist that I am over referring patients with anisocoria. All the patients I refer have physiological anisocoria, need no treatment and are discharged. She told me I was wasting her time and worrying patients unnecessarily. She advised me to go back to my books and work out the difference between pathological and physiological anisocoria. I have tried but am confused. What can I do?

I recently listened to a video learning resource on anisocoria. Unfortunately, it’s behind a firewall so there is no point in me sharing a web link. One presenter was a hospital-based optometrist and the other an ophthalmologist. They explained that they were receiving so many referrals for physiological anisocoria that it was causing patients with pathological abnormalities to have to wait longer for appointments.

They put together some guidance and organised workshops for local primary care eye specialists.

Here are the key points of their guidance:

If the anisocoria increases in dim illumination, then the problem is with the dilator pupil muscle and the eye with the small pupil is the abnormal eye. Referral based solely on anisocoria increasing in dim illumination but mention any ptosis and iris heterochromia. The patient needs a differential diagnosis for Horner’s syndrome.

If the anisocoria is similar in all light conditions and there are normal light and near pupil responses then this is physiological anisocoria and referral is not required.

If the anisocoria increases in bright illumination, then the problem is with the sphincter pupil muscle and the eye with the larger pupil is the abnormal eye. If there is new strabismus and/or the patient complains of diplopia refer urgently. The patient needs a differential diagnosis for a third cranial nerve lesion. If there is no strabismus and/or diplopia then it is a tonic pupil, or a mydriatic drug or iris pathology. Refer routinely for a differential diagnosis.

Following the use of the guidance and the workshops, the quality of the referrals for anisocoria improved significantly.