9/13 Pharmacology of Eye - Walworth

Question 1

location of autonomic receptors on particular tissues of eye

Answer 1

muscles that control the diameter of pupil

• iris dilator: alpha adrenergic → mydriasis
• iris sphincter: Ach muscarinic → miosis

muscles that control accomodation

• ciliary muscle: Ach M
• also puts tension on travecular meshwork to facilitate outflow of aqueous humour

tissue that facilitates secretion of aqueous humour

• ciliary epithelium: beta adrenergic

Question 2

autonomic control of pupil diameter

Answer 2

spinchter pupillae → constriction

• PSNS control via muscarinic receptors

dilator pupillae → dilation

• SNS control via alpha-adrenergic receptors

Question 3

effects of atropine and other antimuscarinic agents of eye

Answer 3

atropine is prototype antimuscarinic agent

• tertiary amine

scopolamine is closely related

• both well absorbed from gut, conjunctiva

pharmaco effects of antimuscarinic excess:

• dry as a bone → decreased secretions/salivation
• blind as a bat → ciliary muscle paralysis (cycloplegia), inability to focus on close objects
• mad as a hatter → CNS excitation
• hot as hell → decr ability to sweat
• red as a beet → cutaneous vasodil
• full as a flask → urinary retention

Question 4

use of autonomic agents for facilitating ophthalmologic exam

Answer 4

• muscarinic receptor antagonists (antimuscarinics)*
• affect: sphincter pupillae m. and ciliary m.

1. tropicamide

• tertiary amine
• mydriatic, cycloplegic
• short duration of action (4-6h…vs 3-7/7-10d for scopolamine/atropine)
• alpha-agonists*
• affect: dilator pupillae m.

1. phenylephrine

• facilitates mydriasis for ophtho exam

Question 5

amblyopia

Answer 5

“lazy eye”

requires extra stimulation to strengthen

atropine can be useful!

• long duration blurring of strong eye to force brain to use/strengthen weak eye

eyepatch might be better…

Question 6

receptors involved in aqueous humour secretion/drainage

link to glaucoma

Answer 6

• beta-adrenergics on ciliary epithelium → secretion of AH
• M on ciliary muscle → outflow of AH

recall: glaucoma is characterized by increased pressure in ant chamber!

• usually due to partially obstructed AH outflow, but sometimes overproduction

Question 7

mechanism of action of pharma agents used in tx of glaucoma

Answer 7

1. beta-blockers

• block receptors on ciliary epithelium → drop AH production → drop IOP

2. muscarinic agonists OR cholinesterase inhibitors

• stim receptors on ciliary m. → increase outflow → drop IOP

Question 8

examples of eye disorders for which pharmaco tx confers benefit

Answer 8

1. age-related macular degen
2. bacterial conjuctivitis
3. dry eyes
4. allergic conjuctivitis

Question 9

special features of eye relevant to pharmaco

Answer 9

1. eye is anatomically isolated

• relative seclusion from systemic access → unusual PD/PK props
  however. ..

2. lacrimal drainage goes to nose, which is lined by highly vascular mucosal epi

• topically applied meds that can pass through have direct access to systemic circ