Adie pupil

**Definition:** Adie tonic pupil = benign neuro-ophthalmic condition from postganglionic parasympathetic denervation of the iris sphincter and ciliary muscle. Adie syndrome (Holmes-Adie syndrome) = tonic pupil + diminished/absent deep tendon reflexes (especially Achilles and patellar).

**Pathophysiology:** - Pathway: Edinger-Westphal nucleus → CN III → ciliary ganglion (in the orbit) → short ciliary nerves → iris sphincter pupillae and ciliary muscle. - Damage to the ciliary ganglion or short ciliary nerves is often viral or postinfectious (suspected), but it can be idiopathic. Other causes include orbital trauma or surgery, ischemia, inflammation, and neuropathies (diabetes, syphilis, sarcoidosis, paraneoplastic). - Aberrant regeneration: Most ciliary ganglion neurons supply the ciliary muscle (accommodation) rather than the sphincter (about 30:1). After injury, regenerating fibers misdirect toward the sphincter. The result is a pupil that constricts with near effort (slowly and tonically) but barely reacts to light, so there is **light-near dissociation**. - Denervation supersensitivity: Up-regulated muscarinic receptors on the sphincter make it respond to dilute cholinergic agonists.

**Clinical features:** - Epidemiology: classically young women (20-40 years), unilateral in about 80% of cases. The second eye may become involved at a rate of roughly 4% per year. - Large (mydriatic) pupil in bright light, with anisocoria greater in light. - Poor or absent direct and consensual light response. Slit-lamp exam shows sector paralysis or vermiform (worm-like) iris movements. - Slow (tonic) constriction to near effort and slow redilation after near effort. - Accommodation problems: blurred near vision, difficulty reading, photophobia. - Hyporeflexia or areflexia of the legs (Holmes-Adie syndrome). Segmental anhidrosis or orthostatic hypotension can occur (Ross syndrome = Adie pupil + hyporeflexia + segmental anhidrosis). - Over time the pupil becomes smaller (**"little old Adie"**) as the sphincter and ciliary muscle fibers gradually recover or fibrosis occurs.

**Diagnosis:** - Dilute pilocarpine (0.0625-0.125%) test: the Adie pupil constricts (supersensitive), and the normal pupil does not. This is the classic board answer. - Rule out other causes of a dilated pupil. A pharmacologic blockade (atropine, scopolamine) does not constrict even with dilute pilocarpine or with 1% pilocarpine. A CN III palsy comes with ptosis and ophthalmoplegia.

**Differential (high-yield):** - CN III palsy: "down and out" eye, ptosis, and a dilated pupil that is unreactive to both light and near. It is a surgical emergency if due to a posterior communicating artery aneurysm. - Pharmacologic mydriasis: no constriction to 1% pilocarpine. - Horner syndrome: miosis, ptosis, anhidrosis. The anisocoria is greater in dark, and it is diagnosed with cocaine or apraclonidine. - Argyll Robertson pupil (neurosyphilis): small bilateral irregular pupils that accommodate but do not react ("prostitute's pupil accommodates but does not react"). It is bilateral and miotic, unlike Adie. - Both Adie and Argyll Robertson show light-near dissociation, but the Adie pupil is large and unilateral.

**Management:** - Reassurance, because the condition is benign. - Dilute pilocarpine drops or reading glasses for accommodation problems or photophobia. Dark or tinted glasses can help with photophobia. - No treatment is needed for the pupil itself.

**High-yield pearls:** Young woman + unilateral dilated pupil + absent knee/ankle reflexes = Holmes-Adie. Lesion at the ciliary ganglion. Supersensitive to dilute pilocarpine. Tonic near response with light-near dissociation.