Examine this patient's eyes.
· Ask the patient about lancinating pains.
· History of multiple sclerosis, sarcoidosis, syphilis.
· Difficulty in walking (remember the gait in tabes dorsalis).
· The pupils are small and irregular.
· Light reflex is absent.
· Accommodation reflex is intact.
· There may be depigmentation of the iris.
· Bilateral ptosis and marked overcompensation by frontalis muscle (in tabes dorsalis).
Proceed as follows:
Tell the examiner that you would like to do the following:
· Examine for vibration and position sense.
· Test for Romberg's sign and deep tendon reflexes (decreased).
· Check syphilitic serology.
· Check urine sugar.
Remember that these pupils show little response to atropine, physostigmine or methacholine.
This patient has Argyll Robertson pupil (lesion) and you would like to investigate for underlying neurosyphilis or leutic infection
What are the causes of Argyll Robertson pupil?
· Neurosyphilis - tabes dorsalis.
· Diabetes mellitus and other conditions with autonomic neuropathy.
· Brainstem encephalitis.
· Multiple sclerosis.
· Lyme disease.
· Sarcoidosis (BMJ 1984; 289: 356).
· 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 (Am J
Ophthalmol 1956; 42: 105). 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
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.
· Blindness or amblyopia in one eye (pupil larger in the affected eye).
· Cerebrovascular accidents.
· Severe head trauma.
· Hemianopia due to optic tract involvement.
Note. Eccentric pupil occurs when the pupil is not in the centre of the iris. It may result from trauma or iritis and need not be
pathognomonic of neurological disease.
Douglas M.C.L. Argyll Robertson (1837-1909) of Edinburgh described these pupils in 1869 with neurosyphilis (Edinb Med J 1869;
15: 487). His studies on the effects of the extracts of the Calabar bean (Physostigma venenosum) on the pupil were widely
acclaimed. He was the President of the Royal College of Surgeons of Edinburgh.