From the Guidelines
Anisocoria is most commonly caused by physiologic anisocoria, pharmacologic agents, Adie's tonic pupil, third nerve palsy, and Horner's syndrome. The condition where pupils are unequal in size can be due to various factors, and it's essential to evaluate the patient thoroughly to determine the underlying cause. According to the study by 1, anisocoria greater than 1 millimeter may indicate a pathological process, such as Horner syndrome, Adie tonic pupil, or a pupil-involving third-cranial-nerve palsy.
Common Causes of Anisocoria
- Physiologic anisocoria, affecting about 20% of the normal population with a difference of less than 1mm between pupils that remains consistent in different lighting conditions
- Pharmacologic agents (like eye drops containing anticholinergics, sympathomimetics, or pilocarpine)
- Adie's tonic pupil (a benign condition resulting from damage to the ciliary ganglion)
- Third nerve palsy (often accompanied by ptosis and eye movement abnormalities), as discussed in the study by 1
- Horner's syndrome (characterized by miosis, ptosis, and anhidrosis due to sympathetic pathway disruption)
Evaluation and Management
When evaluating anisocoria, it's crucial to determine which pupil is abnormal by comparing pupil sizes in both bright and dim light - the abnormal pupil will show less change with light variation. Urgent medical attention is needed if anisocoria is accompanied by headache, vision changes, or neurological symptoms, as this could indicate serious conditions like intracranial hemorrhage or mass lesions. Most cases of isolated anisocoria without other symptoms are benign, but proper evaluation helps distinguish harmless variations from those requiring intervention. As stated in the study by 1, a comprehensive eye examination with particular attention to sensorimotor exam, evidence of ptosis and anisocoria, and pupillary responses in bright and dim illumination is essential in evaluating patients with anisocoria.