Lec 27 Pharmacology of the Eye Flashcards
How is absorption determined after topical eye administration?
- length of time drug stays in cul-de-sac [inferior fornix] and precorneal tear film
How do ocular drugs enter systemic distribution?
via nasal mucosa
What is path of local ocular distribution?
via transcorneal route into aqueous humor to intraocular structures
What determines elimination of eye drug?
nasolacrimal drainage [topical eye drugs can e systemically absorbed]
Does sympathetic or parasympathetic constrict pupil?
parasympathetic
How do you diagnose glaucoma?
- cup diameter is >50% of optic disc diameter
- visual field test [lost periphery]
- IOP [high in glaucoma]
Does zonule relax or contract in accomodation (near vision focus)
zonule relaxes so lens more convex
What is cyclospasm?
severe ciliary muscle contraction
What can block accomodation? term?
muscarinic cholinergic antagonists = not enough PNS
called cycloplegia = inability to accomodate
What causes cyclospasm?
cholinesterase inhibitor toxication = too musc PNS
Does PNS or SNS cause ciliary muscle contraction?
PNS [= for near vision]
Does PNS stimulation or SNS stimulation increase outflow of aqueous humor?
PNS
Where does aqueous humor flow in uveoscleral outflow path?
through ciliary muscles into suprachoroidal space
What is function of B receptors on ciliary epithelium?
promote secretion of aqueous humor
What will happen if you block B receptors on ciliary epithelium?
you will have less aqueous humor produced –> decreased intraocular pressure
What is the predominant B receptor in the eye?
B2
What is the first line medical therapy for glaucoma?
latanoprost
What is mech of latanoprost? side effect?
- type of prostaglandin
- increases aqueous humor outflow via uveoscleral pathway
- side effect: darkens color of iris PLUS its an eye drop so burning, irritation, blurred vision at beginning
What is effect of prostaglandins on eye?
increase outflow of aqueous humor [latanoprost is one]
What is punctuate kerotopathy?
secondary to irritation to preservative in eye drops
What is mech of tumolol? side effects?
- type of beta blocker
- B1/B2 antagonist –> decreases aqueous humor synthesis
- can have systemic side effects [hypotension, bradycardia, dyspnea]
What metabolized B receptor antagonists? significance?
- metabolized by CYP 2D6
Who might you want to avoid giving b receptor antagonists to?
- pt with signficant respiratory disease [asthma or COPD]
- pt on another drug that suppresses CYP 2D6 (since that is what metabolized B antagonists
What is brimonidine?
- alpha 2 agonist
- decreases aqueous humor synthesis via 2 mech [inhibits NE release presynaptically, decreases cAMP pos]
- may also increase outflow
What are side effects of brimonidine?
- blurry vision, ocular hyperemia, foreign body sensation, ocular allergic reaction, ocular pruritis [itching]
What is dorzolamide? side effects?
carbonic anhydrase inhibitor
- decreases aqueous humor synthesis
side effects: opthalmic burning/immune hypersensitivity, metabolic acidosis
What are carbachol/pilocarpine?
direct cholinergic aagonists
- induce muscarinic –> ciliary muscle contraction which helsp aqueous humor outflow
side effects: miosis and cyclospasm [contraction ciliary muscle]
What is echothiphate? why is it not often used?
anticholinesterase agent
- increases PNS activity
- rarely used because causes lens opacity
When is pilocarpine particularly important?
in emergencies –> very effective at opening meshwork into canal of schlemm
