BS - Pupil Function, Malfunction & Assessment - Week 5 Flashcards
What would greater anisocoria in greater light suggest?
A problem with the parasympathetic pathway
What would greater anisocoria in dimmer light suggest?
A problem with the sympathetic pathway
What are 5 causes for irregular pupils?
Trauma Surgery Inflammation Tumour Congenital coloboma
Describe the swinging flashlight test, and what feature of pupil constriction/dilation it relies on.
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.
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?
A marcus gunn pupil, indicating a problem of the afferent pathway.
In what two ways can you elicit mydriasis?
Activate the agonist - noradrenaline or an analog
Inhibit the antagonist - acetylcholine inhibitor
In what two ways can you elicit miosis?
Activate the agonist - acetylcholine or an analog
Inhibit the antagonist - noradrenaline inhibitor
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.
Pilocarpine - emulates ACh, eliciting miosis.
Methacholine - analog of ACh, longer lasting than pilocarpine, eliciting miosis.
What receptor is methacholine specific to?
Muscurinic receptors.
What is a side effect of methacholine?
Athsma
What two secondary actions does pilocarpine have, aside from changing pupil size?
Activates ciliary muscles, and increases accommodation.
Describe the action of physostigmine, and whether it results in miosis or mydriasis.
Elicits miosis by blocking ACh uptake by acetylcholinesterase.
Describe the action of tropicamide, and whether it elicits miosis or mydriasis.
Blocks ACh receptors on the iris sphincter, resulting in mydriasis.
Describe the action of cyclopentolate, and whether it elicits miosis or mydriasis.
Strong and quick blocker of ACh receptors.
Describe the action of atropine, and whether it elicits miosis or mydriasis.
Blocks ACh receptors.
It systematically can block other sites of parasympathetic activity.
Results in mydriasis.
Describe the action of paredrine, and whether it elicits miosis or mydriasis.
Hydroxyamphetamine
Forces the release of noradrenaline, forcing mydriasis.
What effect does paredrine have on ciliary muscles?
Minimal effect.
How does cocaine act, and does it result in miosis or mydriasis?
Inhibits uptake of noradrenaline from the synapse, resulting in dilation.
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?
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
What cocktail is often used to enhance mydriasis?
Phenylephrine (2.5%) and tropicamide, separated by 1 minute for maximum effect.
Name 7 contraindications for inducing mydriasis?
- Narrow anterior chamber angle/angle closure glaucoma
- Ocular injury
- Hyphaemia
- Acute corneal disease
- Hypersensitivity to mydriatic agents
- Pregnancy/lactation
Define hyphaemia.
Haemorrhage into the anterior chamber of the eye.
