Pupil Disorders

Question 1

What is the cause of pupil constriction?

Answer 1

Circular muscles in the iris which cause constriction

These muscles are stimulated by the PS nervous system using acetylcholine as a neurotransmitter

Question 2

Where do the fibres of the Parasympathetic system which innervate the eye travel along?

Answer 2

Oculomotor (CN III) nerve

Question 3

How are dilator muscles of the pupil arranged?

Answer 3

Like spokes on a bicycle wheel

Question 4

What is pupil dilation stimulated by?

Answer 4

Sympathetic nervous system using adrenalin as a neurotransmitter

Question 5

Possible causes of abnormal pupil shape?

Answer 5

• Trauma to the sphincter muscles in iris
• Anterior uveitis can cause adhesions in iris
• AACG
• Rebeosis Iridis (usually assoc with poorly controlled diabetes)
• Coloboma
• Tadpole pupil (assoc with migraine)

Question 6

Causes of mydriasis?

Answer 6

• 3rd nerve palsy
• Holmes Adie syndrome
• Raised ICP
• Congenital
• Trauma
• Stimulants eg cocaine
• Anticholinergics

Question 7

Causes of miosis?

Answer 7

• Horner’s syndrome
• Cluster headaches
• Argyll-Robertson pupil (Neurosyphilis)
• Opiates
• Nicotine
• Pilocarpine

Question 8

What is mydraisis?

Answer 8

Pupil dilation

Question 9

What is miosis?

Answer 9

Pupil constriction

Question 10

Presentation of 3rd nerve palsy?

Answer 10

• Ptosis
• Divergent strabismus
• Dilated non-reactive pupil
• ‘Down and out’ eye position of affected eye

Question 11

What does the oculomotor nerve supply?

Answer 11

Supplies all extraocular muscles except lateral rectus and superior oblique

Question 12

What happens when muscles aren’t getting signals from CN III?

Answer 12

They move outward and downward

Question 13

The oculomotor causes ptosis how?

Answer 13

The nerve also supplies the palpebrae superioris, which is responsible for lifting upper eyelid

Question 14

Which type of fibres does the oculomotor also contain?

Answer 14

Parasympathetic which innervate sphincter muscles of iris, resulting in 3rd nerve palsy causing a dilated fixed pupil

Question 15

The jouney of CN III?

Answer 15

Travels directly from the brainstem to the eye in a straight line
Travels through cavernous sinus & close to posterior communicating artery

Question 16

What 2 things can cause compression on the CN III nerve resulting in 3rds nerve palsy?

Answer 16

Cavernous sinus thrombosis

Posterior communicating artery

Question 17

Causes of 3rd nerve palsy with sparing of pupils ?

Answer 17

Diabetes
Hypertension
Ischaemia

Question 18

What does sparing of pupils in 3rd nerve palsy indicate?

Answer 18

Microvascular causes as PS fibres are spared

Question 19

What is full CN III compression caused by?

Answer 19

Compression of the nerve, including PS fibres compression

Question 20

What may full CN III palsy be caused by?

Answer 20

Idiopathic 
Tumour 
Trauma 
Cavernous sinus thrombosis 
Raised ICP 
Posterior communicating artery aneurysm

Question 21

What is Horner’s syndrome?

Answer 21

Triad of miosis, anhidrosis and ptosis

Question 22

Cause of Horner’s syndrome?

Answer 22

Caused by damage to the sympathetic nervous system supplying face

Question 23

How can the location of Horner’s syndrome be determined?

Answer 23

The anhidrosis

Question 24

What do central lesions cause in Horner’s syndrome?

Answer 24

Central lesions cause anhidrosis of arm and trunk aswell as face

Question 25

What location of Horner's syndrome causes anhidrosis of just the face?

Answer 25

Pre-ganglionic

Question 26

What type of anhidrosis does post ganglionic Horner's syndrome cause?

Answer 26

NO anhidrosis

Question 27

How can Horner's syndrome be remembered?

Answer 27

4 S's (Sentral), 4 T's (Torso/Pre-ganglionic), 4 Cs (Cervical/Post ganglionic)

Question 28

What are sympathetic nerves called when they arise from spinal cord in the chest?

Answer 28

Pre-ganglionic

Question 29

Where do sympathetic nerve enter the sympathetic ganglion?

Answer 29

At the base of the neck and they exit as post-ganglionic nerves

Question 30

What do post-ganglionic nerves travel alongside?

Answer 30

Internal carotid artery

Question 31

Causes of central lesions in Horner's syndrome?

Answer 31

4 S's - Stroke - Multiple sclerosis - Swelling (tumours) - Syringomyelia (cyst in spinal cord)

Question 32

Causes of pre-ganglionic lesions?

Answer 32

4 T's - Tumour (Pancoast's) - Trauma - Thyroidectomy - Top rib (cervical rib growing above 1st rib & clavicle)

Question 33

Causes of post-ganglionic lesions?

Answer 33

4 C's - Carotid aneurysm - Carotid artery dissection - Cavernous sinus dissection - Cluster headache

Question 34

What type of Horner's syndrome is associated with heterochromia?

Answer 34

Congenital Horner Syndrome

Question 35

Investigation for Horner's syndrome?

Answer 35

Cocaine eye drops | Low concentration adrenalin eye drop (0.1%)

Question 36

What do cocaine eye drops convey in the investigation of Horner's syndrome?

Answer 36

Cocaine acts on the eye to stop noradrenaline re-uptake @ neuromuscular junction - Tis causes normal eye to dilate because there is more NA stimulating dilator muscles of iris - In Horner's syndrome, nerves aren't releasing NA, so blocking reuptake doesn't make a difference

Question 37

How do adrenalin eye drops work as an investigation?

Answer 37

Will dilate a normal pupil BUT won't dilate a Horner Syndrome pupil

Question 38

What is Holmes Adie Pupil?

Answer 38

Unilateral dilated pupil that is sluggish to react

Question 39

Presnetation of Holmes Adie Pupil?

Answer 39

Slow dilation of the pupil following constriction | Over time the pupil will get smaller

Question 40

Cause of Holmes Adie pupil?

Answer 40

Damage to post-ganglionic PS fibres | Exact cause unknown but most likely viral

Question 41

What is the Argyll Robertson pupil?

Answer 41

Constricted pupil that accommodates when focusing on a near object but does not react to light Often irregularly shaped

Question 42

What disease is Argyll Robertson pupil a common finding in?

Answer 42

Neurosyphilis

Question 43

What is another common name for Argyll Robertson pupil?

Answer 43

Prostitutes pupil | Because of relation to syphilis and because it accommodates but doesn't react