BS - Pupil Function, Malfunction & Assessment - Week 5

Question 1

What would greater anisocoria in greater light suggest?

Answer 1

A problem with the parasympathetic pathway

Question 2

What would greater anisocoria in dimmer light suggest?

Answer 2

A problem with the sympathetic pathway

Question 3

What are 5 causes for irregular pupils?

Answer 3

Trauma
Surgery
Inflammation
Tumour
Congenital coloboma

Question 4

Describe the swinging flashlight test, and what feature of pupil constriction/dilation it relies on.

Answer 4

The slow dilation of the pupil when light is removed allows one to perform the swinging flashlight test, where light is flshed onto the eyes quickly and sequentially.

Question 5

If, during a swinging flashlight test, and eye is illuminated, and the pupil constricts. The second eye is then quickly illuminated, but it now dilates instead of constricting. What is this called, and what problem does it indicate?

Answer 5

A marcus gunn pupil, indicating a problem of the afferent pathway.

Question 6

In what two ways can you elicit mydriasis?

Answer 6

Activate the agonist - noradrenaline or an analog

Inhibit the antagonist - acetylcholine inhibitor

Question 7

In what two ways can you elicit miosis?

Answer 7

Activate the agonist - acetylcholine or an analog

Inhibit the antagonist - noradrenaline inhibitor

Question 8

Describe the effects of pilocarpine and methacholine.
Indicate whether it acts on the sympathetic or parasympathetic system, for mydriasis or miosis.
State which is longer lasting.

Answer 8

Pilocarpine - emulates ACh, eliciting miosis.

Methacholine - analog of ACh, longer lasting than pilocarpine, eliciting miosis.

Question 9

What receptor is methacholine specific to?

Answer 9

Muscurinic receptors.

Question 10

What is a side effect of methacholine?

Answer 10

Athsma

Question 11

What two secondary actions does pilocarpine have, aside from changing pupil size?

Answer 11

Activates ciliary muscles, and increases accommodation.

Question 12

Describe the action of physostigmine, and whether it results in miosis or mydriasis.

Answer 12

Elicits miosis by blocking ACh uptake by acetylcholinesterase.

Question 13

Describe the action of tropicamide, and whether it elicits miosis or mydriasis.

Answer 13

Blocks ACh receptors on the iris sphincter, resulting in mydriasis.

Question 14

Describe the action of cyclopentolate, and whether it elicits miosis or mydriasis.

Answer 14

Strong and quick blocker of ACh receptors.

Question 15

Describe the action of atropine, and whether it elicits miosis or mydriasis.

Answer 15

Blocks ACh receptors.
It systematically can block other sites of parasympathetic activity.
Results in mydriasis.

Question 16

Describe the action of paredrine, and whether it elicits miosis or mydriasis.

Answer 16

Hydroxyamphetamine

Forces the release of noradrenaline, forcing mydriasis.

Question 17

What effect does paredrine have on ciliary muscles?

Answer 17

Minimal effect.

Question 18

How does cocaine act, and does it result in miosis or mydriasis?

Answer 18

Inhibits uptake of noradrenaline from the synapse, resulting in dilation.

Question 19

What percentage of phenylephrine is commonly used for which change in pupil size?
At how many minutes post administration does maximal change occur?
How long does it last for?
What side effects can it have?

Answer 19

2.5% typically used.
Maximum dilation/mydriasis occurs at 35-45 minutes post administration
Lasts for 3-6 hours
Has cardiovascular side effects, including cardiac disease and tachycardia

Question 20

What cocktail is often used to enhance mydriasis?

Answer 20

Phenylephrine (2.5%) and tropicamide, separated by 1 minute for maximum effect.

Question 21

Name 7 contraindications for inducing mydriasis?

Answer 21

• Narrow anterior chamber angle/angle closure glaucoma
• Ocular injury
• Hyphaemia
• Acute corneal disease
• Hypersensitivity to mydriatic agents
• Pregnancy/lactation

Question 22

Define hyphaemia.

Answer 22

Haemorrhage into the anterior chamber of the eye.