Adie syndrome

Overview

Adie syndrome, also known as Adie’s tonic pupil or simply tonic pupil, is a rare neurological condition that primarily affects the eye and autonomic nervous system. It is characterized by a unilateral, abnormally dilated pupil that reacts slowly to light but may constrict more noticeably during near vision (accommodation). It often affects young women and is usually benign, although it may occasionally be associated with diminished reflexes or autonomic dysfunction. The condition typically affects only one eye but can be bilateral in rare cases.

Causes

Adie syndrome is caused by damage to the postganglionic fibers of the parasympathetic nervous system that innervate the eye’s pupil via the ciliary ganglion. The exact cause of this damage is often unknown (idiopathic), but possible contributing factors include:

• Viral infections

• Bacterial infections

• Trauma to the orbit or head

• Inflammatory or autoimmune conditions

• Neuropathy (e.g., due to diabetes or alcoholism in rare cases)

Symptoms

The hallmark feature of Adie syndrome is a tonically dilated pupil. Additional symptoms may include:

• One pupil larger than the other (anisocoria)

• Slow or absent reaction to bright light

• Better constriction with near focus (light-near dissociation)

• Blurred vision or difficulty reading at close distances (due to loss of accommodation)

• Photophobia (light sensitivity)

• Diminished or absent deep tendon reflexes (especially the Achilles reflex), seen in the variant known as Holmes–Adie syndrome

The condition is usually painless and develops gradually. Many individuals may not notice the pupil abnormality until it is incidentally discovered.

Diagnosis

Diagnosis of Adie syndrome is based on clinical findings and specific eye examination techniques. Key diagnostic tools include:

• Pupillary light reflex test: Shows poor reaction to light but better response to near vision

• Pilocarpine test: A dilute solution (0.125%) of pilocarpine causes the tonic pupil to constrict abnormally due to denervation hypersensitivity, while the normal pupil shows little to no response

• Slit-lamp examination: Reveals segmental contraction of the iris sphincter

• Neurological examination: To assess for associated reflex abnormalities or autonomic dysfunction

Further investigations may be performed to rule out other causes of anisocoria, such as Horner syndrome, third nerve palsy, or pharmacologic dilation.

Treatment

There is no cure for Adie syndrome, but treatment is usually not necessary unless symptoms are bothersome. Management options include:

• Reading glasses or bifocals: To address difficulty with near vision

• Pilocarpine eye drops: Low-dose pilocarpine may be used to improve near focusing and reduce pupil size

• Tinted lenses or sunglasses: To help with light sensitivity

• Physical therapy: In cases where deep tendon reflexes are affected and functional issues arise (rare)

Prognosis

The prognosis for Adie syndrome is generally excellent. It is a benign condition and does not lead to vision loss or life-threatening complications. Over time, the pupil may become smaller (referred to as “little old Adie’s pupil”) and the symptoms often become less noticeable. If the condition is bilateral or associated with autonomic dysfunction, more careful monitoring may be required, but overall long-term outcomes are favorable.