Authors: Dr Özge Can , Dr Pinar Baran , Dr Sadiye Midik , Prof Murat Ersel

Abstract

Introduction: Anisocoria is a significant clinical sign that may indicate serious neurological conditions such as third cranial nerve palsy, intracranial hemorrhage, or uncal herniation. However, it can also be caused by benign disorders like Adie-Holmes syndrome. Adie pupil is characterized by a tonically dilated pupil with poor or absent light reaction and preserved, though often slow, near response. It is caused by postganglionic parasympathetic denervation at the level of the ciliary ganglion. The condition typically affects young women and is unilateral in 80% of cases. When accompanied by diminished or absent deep tendon reflexes, the condition is referred to as Adie-Holmes syndrome. We report a case of a man diagnosed with Adie pupil after comprehensive emergency evaluation.

Case:A 39-year-old man presented to the emergency department with the complaint of blurred vision and a dilated right pupil noticed on awakening.  He denied any history of trauma, headache, diplopia, nausea, or systemic illness. His vital signs were within normal limits. Neurological examination revealed normal motor and sensory function with intact cranial nerves, except for anisocoria. The right pupil was enlarged, and nonreactive to light. The left pupil was normal in size and response (Picture 1).

Ophthalmology consultation was requested. Optical coherence tomography revealed retinal nerve fiber layer (RNFL) thickness of 87 μm in the right eye and 86 μm in the left, within normal limits. A non-contrast cranial CT was performed as part of the differential diagnosis to rule out acute intracranial pathology, and results were unremarkable. Given the persistent anisocoria and absence of mass lesion, a contrast-enhanced cranial MRI was obtained, which was also normal.

To further investigate the etiology, the patient was referred to the neuro-sensory laboratory where dilute pilocarpine testing was performed. The patient was diagnosed with Adie pupil syndrome and discharged with outpatient follow-up recommendations in neuro-ophthalmology.

Discussion and Conclusion: Adie syndrome is generally idiopathic but may rarely be linked to infections (e.g., syphilis, varicella, Lyme disease), autoimmune diseases (e.g., Sjögren’s, lupus), or neoplastic processes. The key pathophysiology involves degeneration in the ciliary ganglion, leading to cholinergic denervation hypersensitivity of the iris sphincter. This explains the pupil’s abnormal response to light and positive reaction to dilute pilocarpine.

In the acute setting, it is crucial to exclude life-threatening causes of anisocoria. Neuroimaging should be considered when patients present with headache, diplopia, ptosis, or neurologic deficits. In our case, normal cranial CT and contrast-enhanced MRI ruled out structural brain lesions. Normal RNFL thickness further excluded optic nerve pathology. The diagnosis was confirmed by a positive pilocarpine test.

Adie syndrome may also involve progressive areflexia and autonomic dysfunction such as segmental anhidrosis, known as Ross syndrome. Although our patient did not show these features initially, long-term follow-up is recommended due to the possibility of progression.

Conclusion: Adie-Holmes pupil is a rare but important differential diagnosis in patients presenting with unilateral mydriasis. Emergency physicians should be familiar with its clinical features and diagnostic approach to prevent unnecessary interventions and to provide appropriate referrals.

Keywords: Anisocoria, Adie Pupil, Tonic pupil