Argyll Robertson pupil Frequently Asked Questions

What are the causes of Argyll Robertson pupil?
· Neurosyphilis - tabes dorsalis.
· Diabetes mellitus and other conditions with autonomic neuropathy.
· Pinealoma.
· Brainstem encephalitis.
· Multiple sclerosis.
· Lyme disease.
· Sarcoidosis.
· Syringobulbia.
· Tumours of the posterior portion of the third ventricle.

What do you know about the nerve pathways of the light reflex?
· The afferent is through the optic nerve and the efferent limb is through the third cranial nerve. The relevant optic nerve fibres responsible for the light reaction leave those responsible for the perception of light to terminate in the pretectal region of the midbrain, from whence a further relay passes to the Edinger-Westphal nucleus.
· Disturbances of the pupillary light reflex occur when there is involvement of the following:
- Superior colliculus.
- Decussation of Meynert.
- Edinger-Westphal nucleus (supplies the constrictor muscles of the iris).

Where is the lesion in Argyll Robertson pupil?
Damage to the pretectal region of the midbrain is believed to be responsible for the Argyll Robertson pupil of neurosyphilis . This, however, does not explain the small irregular pupils and it has been suggested that local involvement of the iris is a separate lesion.

Which muscle in the eye is responsible for the accommodation reflex?
Paralysis of accommodation occurs when the ciliary muscle is involved. Remember that accommodation is a much more potent stimulus for constriction of the pupils than light, as there are more nerve fibres mediating the accommodation reflex than the light reflex.

Mention a few causes of a small pupil?
· Senile miosis.
· Pilocarpine drops in the treatment of glaucoma.

What is 'reversed' Argyll Robertson pupil?
The pupils react to light but not to accommodation - seen in parkinsonism caused by encephalitis lethargica.

What do you understand by the term 'anisocoria'?
Anisocoria is gross inequality of the pupils. Causes include:
· About 20% of normal individuals.
· Third nerve palsy.
· lritis.
· Blindness or amblyopia in one eye (pupil larger in the affected eye).
· Cerebrovascular accidents.
· Severe head trauma.
· Hemianopia due to optic tract involvement.