Pharmacology of the eye Flashcards
What are the 3 components of the uveal tract?
iris
ciliary body
choroid
What is the landmark separating the eye into anterior and posterior chambers?
The lens
What ocular reflex is a tool for assessing brain damage? What happens to the eye in low light? WHat happens in a lot of light?
The consensual pupil response
Mydriasis
Miosis
What is the mechanism by which mydriasis occurs? What is the mediating receptor?
Contraction of radial smooth Muscle
Alpha 1 receptors expressed on radial smooth muscle
What 2 drug classes can cause mydriasis?
Muscarinic antagonist
Alpha 1 agonist
What is the mechanism by which myosis occurs? What is the mediating receptor?
Contraction of the sphincter smooth muscle
M3 muscarinic receptors on iris
What are 2 drug classes that can cause myosis?
M3 muscarinic agonist
Opioids
What is the structure that governs accomodation in the eye? What structure controls it and how?
The lens govern accomodation
Ciliary muscle attaches to lens via suspensory ligaments
What happens when the ciliary muscle relaxes? Contracts?
Relaxes - Decreased lens radius - farsighted
Contracts - Increased lens radius - near sighted
What drug class will improve / increase accomodation?
Muscarinic agonist
How are the effects of adrenergic and muscarinic agents differ in the eye?
Adrenergic agents cause only mydriasis
Muscarinics antagonists can cause mydriasis and cycloplegia
What is the effect of adrenergic agonists on the ciliary muscle?
Nothing - no receptors expressed on them
Where is aqueous humor produced?
From blood vessels in the eye, flows into anterior chamber before draining
What are 2 receptors that can be activated to decrease the production of aqueous humor?
Alpha 1 and alpha 2, decrease blood flow and resulting aqueous humor production
What is a receptor that can be activated stimulated to increase production of aqueous humor?
Beta 1 receptors
What aspect of the eye can potentially bind drugs and affect their concentrations / distribution?
Melanin in the iris
What can be used to detect corneal lesions or foreign bodies in the eye?
Fluorescent dyes
What is the effect of muscarinic antagonists on the eye? Which Receptor subtype is targeted and where are they expressed?
Mydriasis
M3 on the iris and ciliary muscle
What causes glaucoma? What are the 2 factors that determine whether it develops or not?
Poor drainage of aqueous humor
- rate of aqueous humor production
- rate of drainage
Open angle glaucoma is a chronic / acute disease? What causes it?
Chronic disease
Inadequate drainage from the canal of schlemm
Would you want to stimulate or block beta receptors to treat glaucoma? What is the effect?
Inhibit
Block beta 1 on the ciliary body
Would you want to stimulate or block alpha receptors to treat glaucoma? What is the effect?
Stimulate
Stimulates alpha 2 on ciliary body, alpha 1 on ciliary vessels
What is closed angle glaucoma? What causes it?
Rapid increase in intraoccular pressure
Iris grows towards cornea, impeding outflow
What are 2 miotic producing drugs that can be used to treat closed angle glaucoma?
Pilocarpine
Carbachol
What is the effect of mydriasis on closed angle glaucoma?
It worsens it
What can be used to treat squint and blepharospasm? How does it work?
Botulinum toxin A
It blocks releases of neurotransmitter, causing muscle relaxation (3-6 weeks)
Why aren’t the effects of bethanechol potentiated by an AchE inhibitor?
Because bethanechol isn’t a substrate for AchE in the first place
The tracing of MAP in response to Epi or norepi is usually biphasic, a first small spike followed by a reduction and then a larger more prolonged spike. What causes these 3 things?
Small spike - Due to Beta 1 receptos
Reduction -due to vagal reflexes
Prolonged increase - Due to alpha 1
The MAP tracing from Epi but not NE has an overshoot at the tail end of its effects. What mediates this?
Beta 2 receptors, activated by Epi but not NE
If you wanted to block the vagal reflex that causes the initial reduction in MAP following NE or Epi infusion, what can you use?
A ganglionic blocker (Mecamylamine or Trimethaphan)
