Patient reports abnormal light sensitivity, blurred vision, difficulty focusing, or that the abnormal pupil was detected only when looking in the mirror or incidentally on a medical examination
One pupil or both pupils may be affected
In dim light, the affected pupil may be larger or smaller than the unaffected pupil
Affected pupil constricts minimally to a direct light and slowly to a near target (“tonic light-near dissociation”)
Affected pupil dilates slowly as fixation is directed from a reading target to a distant target (“tonic redilatation”)
Segmental iris sphincter palsy is visible as an irregular pupil shape and uneven constriction of the iris when the patient views a near target (“stromal streaming”)
Possible accompanying clinical features
Subtle iris transillumination defects (iris atrophy) visible on slit-lamp examination
Reduced accommodation in younger patients, often mild and quickly resolving
Reduced corneal sensation in the affected eye
Reduced or absent deep tendon reflexes (“Holmes–Adie syndrome”)
Peripheral neuropathy, dysautonomia
History of retinal buckle/photocoagulation, cyclocryotherapy, orbital tumor/trauma/surgery
Be sure that there are no ocular ductional deficits, misalignment, or ptosis, which would suggest third nerve palsy
Be sure there are no features to suggest a diagnosis of peripheral neuropathy or systemic dysautonomia
Look for these pupillary abnormalities (aided by slit lamp examination)
Light-near dissociation
Slow (tonic) pupil constriction and redilatation
Segmental palsy with stromal streaming
If clinical features are not diagnostic, instill dilute (0.1%) pilocarpine into both eyes, wait 30 minutes, and look for miosis in the affected eye (“cholinergic denervation supersensitivity”)
If no denervation supersensitivity is present, instill 0.5% pilocarpine in the affected eye, wait 30 minutes, and look for lack of constriction of the affected pupil, which would suggest a diagnosis of pharmacologic mydriasis or iridoplegia
Prescribe bifocal glasses if the patient has lingering deficient accommodation
Caregivers often miss this diagnosis, incorrectly assuming that it reflects third nerve palsy or incipient brain herniation, which elicits unnecessary brain imaging
Patients should be reassured and advised of the following prognosis
Accommodation will recover fully within weeks
The affected pupil will become smaller within months but never regain normal constriction to light
If only one eye is affected at presentation, the other eye may become affected within months to years
There will be no lingering ophthalmic symptoms or future neurologic or systemic consequences if not already present