Testing the Visual System Tutorial

Question 1

58M - inability to open right eye. Eye is deviated down and out. Complains of double vision when eyelid is lifted. On H-test he cannot elevate or adduct his right eye. His left eye has normal movements in all directions. His right pupil is also dilated in comparison to the left. He has a normal direct and consensual light response.

Which cranial nerve may account for this presentation?

Answer 1

Unable to move down and out
- CN III = oculomotor (supplies all the other muscles

Unable to lift eyelid - levator palpebrae = supplied by CN III

VI - lateral lectus
IV - superior oblique

Question 2

What pathologies may cause this?

Answer 2

Lesion
Aneurysm (posterior communicating artery) - although this present with pain
Head injury
Infection - rare, abscess affecting the nerve
Brain tumour
Oculomotor nerve palsy
Autoimmune
Small vessel diseases - diabetes, hypertension, vascular heart disease

Question 3

How do tumour lesions and vascular lesions present differently?

Answer 3

Pupil fibres run on the outside of the nerve

Tumour = more likely to compress pupil fibres
Vascular = multiple blood supplies to pupil so may not be ass affected

Question 4

What treatments may be offered for this presentation?

Answer 4

NSAIDs for pain

If congenital, treat underlying cause
If acquired, treat underlying cause

Question 5

28F - tonically dilated pupil in the right eye. Right pupil slower to react than the left. The left eye reacts when light is shone into the right eye. Addition of pilocarpine drops, however, causes rapid constriction of the right pupil. On further examination, she has an absent knee-jerk reflex and impaired sweating.

What is the site of damage causing the pupil defect?

Answer 5

Adie pupil - commonly affects young women
Loss of parasympathetic supply

Adie Syndrome = pupil is larger than normal (dilated) and slow to react in response to direct light. Absent or poor tendon reflexes are also associated with this disorder.

Question 6

What is the site of damage causing the absent reflex and impaired sweating?

Answer 6

Holmes Adie - damage to the dorsal root ganglion

Question 7

How does pilocarpine work?

Answer 7

Causes cholinergic denervation and supersensitivity (sharp increase of sensitivity of post-synaptic membranes to a chemical transmitter after denervation) of the pupil = rapid constriction of the pupil, and it is more constricted than a normal pupil

Question 8

What term can be used to describe this defect?

Answer 8

Adie Syndrome