BS - Pupil Disorders - Week 4

Question 1

What is the difference between an afferent and efferent pathway?

Answer 1

Afferent - eye to CNS

Efferent - CNS to eye via ANS

Question 2

What are the two types of efferent pathways to the eye?

Answer 2

Sympathetic

Parasympathetic

Question 3

Name 4 innervational problems to the iris.

Answer 3

Anisocoria
Abnormal:
-Direct
-Consensual
-Near

Question 4

Describe the parasympathetic pathway to the iris (4), the effect on the pupil, the neurotransmitter used, and the receptor type (2).

Answer 4

Begins at the Edinger-Westphal nucleus, leaving with CN3
Travels to the ciliary ganglion (CN5)
Travels via the short ciliary nerve to the sphincter pupillae
Causes constriction
Uses Ach neurotransmitter
Nicotinic receptors are used at the ciliary ganglion
Muscarinic receptors are used at the iris

Question 5

Where is the ciliary ganglion found in relation to the eye?

Answer 5

Just behind the eye temporally

Question 6

Describe the sympathetic pathway to the iris (8), the effect on the pupil, the neurotransmitter used, and the receptor type (2).

Answer 6

Originates from the thalamus/hypothalamus in the midbrain.
Preganglionic fibres travel to the ciliospinal centre at T1 via the long ciliary nerve.
An interneuron relays to the superior cervical ganglion from T1.
Postganglionic fibres start at the superior cervical ganglion and follow the carotid plexus, through the cavernous sinus, to the dilator pupillae muscle.
It dilates the iris.
Uses Ach neurotransmitter.
Nicotinic receptors are used at the superior cervical ganglion
Adrenergic receptors are used at the iris

Question 7

Consider an eye with RAPD/Marcus Gunn pupil. List 7 pathologies that would indicate the problem is before the chiasm.

Answer 7

Large retinal detachment
Central retinal artery occlusion
Central retinal vein occlusion
Optic nerve ischaemia
Asymmetric glaucoma
Optic neuritis
Optic nerve compression

Question 8

Which of the following do not cause RAPD?
Cataracts
Vitreous haemorrhage
Amblyopia

Answer 8

All of them

Note - amblyopia may present a mild RAPD

Question 9

True or false

Anisocoria is a feature of RAPD

Answer 9

False, it is not a feature

Pupil sizes are equal in light and dark

Question 10

Describe how both pupils react in a swinging flashlight test in someone with RAPD.

Answer 10

Normal eye - regular small relaxation after initial constriction
Affected eye - both pupils dilate

Question 11

Describe video pupillometry.

Answer 11

An infrared camera is used to automate pupil size measurement.

Question 12

How do the following conditions affect constriction and relative escape?
Brighter
Dimmer
Diseased eye

Answer 12

Brighter - more constriction, less relative escape
Dimmer - less constriction, more relative escape
Diseased eye - less light delivered=less constriction, more relative escape

Question 13

What is meant by relative escape in pupillometry?

Answer 13

Consider a normal pupil response vs a diseased eye pupil response.
The difference between the two recovery phases after constriction is the relative escape.

Question 14

Differentiate between a mild and severe RAPD pupillometry response.

Answer 14

After shining light into the good eye, it will drive a consensual response in the affected eye.
Mild - affected eye has some constriction will occur, but less than the good eye, and will have an early escape (quicker dilation).
Severe - affected eye has no constriction

Question 15

What three sites are suspected of injury if there is an RAPD?

Answer 15

Gross retinal pathology
Optic nerve pathology
Pre-brainstem optic tract pathology

Question 16

Describe the 5 grades of RAPD.

Answer 16

No RAPD (0) - pupils constrict and show equal physiological escape
+1 - affected eye escape after 3 seconds only
+2 - affected eye escape after 2 seconds only
+3 - affected eye escape after 1 seconds only
+4 - immediate affected eye escape

Question 17

True or false

An efferent pathway dysfunction never causes anisocoria

Answer 17

False, it does

Question 18

True or false

An afferent defect NEVER causes anisocoria

Answer 18

True

Question 19

Consider the sympathetic efferent pathway. How many interneurons does it have, where are they located, and what 4 structures do they supply?

Answer 19

3 interneurons, 2 CNS, 1 periphery
Supplies:
-Pupil dilator (dark)
-Muller muscle (lids)
Facial sweat glands
Ocular blood vessels

Question 20

Which dermatome is the Edinger-Westphal nucleus found? What about the ciliary ganglion?

Answer 20

EWN - C

Question 21

What 2 things does the parasympathetic efferent pathway supply, and what three reflexes does it produce?

Answer 21

Sphincter pupillae
Vergence/accommodative input
Produces the D, C, N reflexes

Question 22

True or false

Innervation problems ALWAYS give abnormal pupil reflexes

Answer 22

True

Question 23

The following indicate a problem with which pathway?
Greater anisocoria in the dark
Greater anisocoria in the light
Name which pupil and muscle would be the defective one.

Answer 23

Light - parasympathetic problem, sphincter pupillae doesnt constrict, defective pupil is the larger one

Dark - sympathetic problem, dilator action is weak, defective pupil is the smaller one

Question 24

Describe what is meant by dilation lag, and what it is a characteristic sign of?

Answer 24

The anisocoria is most evident during the first 4-5 seconds of being in dim conditions. The affected eye (smaller one) will slowly dilate or ‘lag’ over 10-15 seconds, making the anisocoria less evident.
It is characteristic of Horner’s syndrome

Question 25

If dilation lag is observed, what 6 other pathologies should be looked for, and what condition do they indicate?

Answer 25

Ptosis
Facial anhydrosis
IOP reduced on the affected side
Conjunctival flush
Increased accommodation (1.00D)
Iris heterochromia (congenital/very long standing)
They are indicative of Horner's syndrome

Question 26

Suppose dilation lag and iris heterochromia is seen, what condition does this indicate, and why does it present with iris heterochromia?
What two additional pathologies are seen with this condition?

Answer 26

Congenital Horner's syndrome
This is due to sympathetic innervation being needed to develop iris pigmentation
Additionally causes:
Brachial plexus trauma
Forceps delivery at birth

Question 27

Consider a parasympathetic dysfunction. How can a mid-brain lesion be differentiated from a peripheral lesion (4)?

Answer 27

Mid-brain lesion will result in the following:
No light reflex to light
Near reflex observed

Peripheral lesion will result in the following:
No light or near reflex

Question 28

Name 2 conditions that can cause a mid-brain lesion.

Answer 28

Syphilis

Parinauds (aqueductal stenosis)

Question 29

Name 4 conditions that can cause a peripheral lesion.

Answer 29

Iris trauma (increased IOP)
CN3
Drug usage
Viral (Adies: HZV)

Question 30

Consider an individual with Parinaud’s syndrome. What pathway defect do they have, where is the lesion, and describe what it can be caused by, and any eye conditions they might have aside from a defective pupil.

Answer 30

Parasympathetic pathway defect
Mid-brain lesion (posterior)
Can be due to pineal tumour
Have nystagmus on attempted gaze

Question 31

Consider an individual with an Argyll Robertson pupil. What pathway defect do they have, where is the lesion, and describe what it can be caused by, and any eye conditions they might have, including their reaction to light.

Answer 31

Parasympathetic pathway defect
Mid-brain lesion, supra-nuclear Edinger-Westphal lesion in the descending pathways
Pupils are irregular and miotic
Total absence of light response
Brisk near response
Affects both sides of the EW to give a smaller pupil
Can be caused by syphilis

Question 32

Describe a light and near dysfunction, what conditions it is most apparent in, and its most common cause. Describe why a lack of near response is a good thing (2), and what response is often seen.

Answer 32

Poorly responsive, large pupil to light and near.
Most apparent in bright light.
Adies is the most common cause.
Lack of near is good because it means:
-peripheral cause
-no light near dissociation
Often a tonic response.

Question 33

Consider a peripheral ANS lesion. What effect does this have?

Answer 33

Muscle on the involved side becomes suprasensitive to agonists (Adrenaline/Ach)

Question 34

Consider a sympathetic ANS lesion. What two drugs would be used to determine this?

Answer 34

Phenylephrine 2.5%

Aprachlonidine 0.5%

Question 35

Consider a parasympathetic ANS lesion. What drug would be used to determine this?

Answer 35

Pilocarpine 1%

Question 36

What effect does low dose pilocarpine have on a normal pupil vs an Adies pupil, and what does this suggest?

Answer 36

Little effect in normal eyes, but a marked effect in Adies pupils, suggesting parasympathetic dysfunction.