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miotics and mydriatics
Terms in this set (35)
what structures in. the eye receive cholinergic. innervation?
give the origin and pathway of. cholinergic supply to the. eye. structures?
innervation of the ciliary body and sphincter muscle originates in the EWN
(pregang emerges from EWN, exit the CNS through CN3 and go to ciliary gang, then synapse with post gang fibers and enter the globe. through. short ciliary nerves, they. terminate on muscarinic receptors in. the iris sphincter and ciliary body)
Lacrimal gland also receives parasympathetic innervation (pregang fibers travel with. CN7, synapse with sphenopalatine gang, post gang fibers become part of the fifth nervew and pass to. the lacrimal gland through the lacrimal nerve)
what are the cholinergic agonists and their other names?
-produce biologic responses similar to those of acetycholine
also known as parasympathetics or cholinometics
how are cholinergic agonists classified? identify drugs in each class
they are classified according to their mechanism of action
how do direct acting adn indirect acting cholinergic agonists work?
DIRECT activate cholinergic receptors directly at the neuroeffector jxs of the iris sphincter muscle and ciliary body
INDIRECT exert their cholinergic effects primarily by. inhibiting cholinesterase therefore increasing the amount of acetylcholine available at cholinergic receptors
give the 3 responses of intraocular smooth muscle to pilocarpine (which acts at both peripheral adn central muscarinic sites)
spasm of accommodation
reduction of iop
what. is teh mechanism involved in pilocarpine induced increase in aqueous outflow?
direct stimulation of the longitudinal muscle of the ciliary body-->pulled scleral spur widens the trabecular spaces-->increase in aqueous outflow
what are the. risks associated due. to. long term therapy. with pilocarpine?
alters iris muscle activity
may cause permanent miosis due to loss of iris radial muscle tone and fibrosis of the sphincter muscle
give the. dosage forms, strengths of formulations adn recommended dosage of pilocarpine?
available as an ophthalmic solution in concentrations from 0.25% to 10%
also available as 4% ophthalmic gel
1, 2, 4% are the most commonly prescribed concentrations
solutions typically four times a day
gel=1/2 ribbon in lower conj sac
what is the iop at which pilocarpine does not respond? what agents are administered to bring down the. iop to make pilocarpine respond?
when iop is greater than 60mmhg iris sphincter will be unresponsive to pilocarpine
topical beta blockers, apraclonidine are used initially to bring iop below 50mmhg
what are the main clinical uses of pilocarpine?
acute angle closure glaucoma
utilized after an angle closure attack in prep of pt for laser peripheral iridotomy
1% solution to dx CN3 palsy from a sphincter tear
0.125% solution is used to dx adies tonic pupil
what. are the main ocular side effects of pilocarpine?
what are the contrainndications to pilocarpine use?
those with cataracts
pts younger than 40 years of age(can cause refractive probs)
neovascular and uveitic glaucoma
hx of ret detachment
what are t he advantages and drawbacks of carbachol compared to pilocarpine?
-completely resistant to hydrolysis by cholinesterases(AChE or BuChE)
-exerts less miotic action than pilocarpine
-poorly lipid soluble, therefore its intraocular bioavailability is considerably less than pilocarpine
-carbachol has more severe local side effects than pilocarpine
give the clinical applications of. carbachol
-lowers iop in primary adn secondary open angle glaucomas
-is available for intraocular use to produce miosis during surgery
-its action is prolonger adn instilled less frequently than shorter acting miotics
give. the main clinical applications of
used in diagnosis of myasthenia gravis(if ptosis improves then affirms mya grav)
NEOSTIGMINE (prostigmin), PYRIDOSTIGMINE (mestinon)
treatment of myasthenia gravis
used for diagnosis and/or treatment of accommodative esotropia and rarely for glaucoma
list 4 main adverse systemic effects of miotics
what are mydriatics? give. ocular functions. that they regulate
drugs that stimulate the adrenergic divisino of ans
also called sympathomimetics or adrenergic agonists
-width of palpebral fissure
-diameter of ocular blood vessels
-aqueous flow and accommodation
what is the pathway involved in adrenergic. innervation to the eye?
originates from the posterior and lateral nuclei of the hypothalamus--->unmyelinated fibers cross over the sixth cranial nerve and join the ophthalmic division of the trigeminal nerve--->fibers bypass the ciliary ganglion and accompany the long ciliary nerves to
-iris dilator muscle
-muellers muscle of. the eyelid
compare the sympathetic and parasympathetic. input to the eye
is inhibitory in nature and mediated via beta adrenergic receptors
the input is relatively small with respect to para output
the time course of the sympathetic activity is significantly slower than that of para
symp activity appears to be augmented by concurrent parasymp. activity
categorize the key cholinergic receptors in terms of their location and effects
lacrimal gland-M2, M3-increase tear production
give the receptor involved , mechanism and pharmacological effects of phenylephrine?
acts primarily on alpha 1 receptors, no. effect on. beta receptors
?release of norepinephrine from adrenergic nerve terminals?
-iris dilator muscle
-smooth muscle of the conjunctival arterioles
blanching of conj
stimulation of muellers muscle of upper lid
decrease in iop
what is the instability of phenylephrine and how is it overcome?
is subject to oxidation on. exposure to. air, light, or heat
sodium bisulfite (an antioxidant) is frequently added to. vehicle to prolong shelf life
what is teh. response of dark irides to phenylephrine?
dark irides have a greater frequency of poorer dilation than do light irides
give the main clinical uses of phenyephrine
a valuable aid in breaking posterior synechiae
10% solution used for peripheral corneal vessel vasoconstriction during LASIK refractive sx
2.5% solution. used concomitantly with echothiophate to prevent the formation of miotic cysts during oag or esotropia treatment
ptosis from horners
give the key ovular side effects and contraindications phenylephrine
pigmented aqueous floaters
rebound conj congestion
idiopathic othostatic hypotension
insulin dependent diabetes
also contraindicated in pts taking MAO inhibitors, tricyclic antidepressants, reserpine, guanethidine or methyldopa
use 2.5% in infants or elderly
prolonged irrigation or subconj injection of 10% solution is not recommended
how does hyroxyamphetamine work and what are the receptors involved?
is an indirect acting adrenergic agonist
its primary pharmacologic action is due to release of norepinephrine
directly stimulates alpha receptor mainly and possibly beta receptor sites
does not raise iop in eyes with open anterior chamber angles
compare the efficacy of hydroxyamphetamine to 2.5% phenelyephrine
-produce nearly equal amount of pupillary dilation
-show maximum effect at approx 45 minutes
what is the composition of paremyd? give its advantages
combination of this, paremyd, with hydroxyamphetamine 1% causes greater mydriatic efficacy than adrenergic agonist alone or tropicamide 0.5% or 1%
paremyd has a mydriatic efficacy equivalent to that of phenlyephrine 2.5% followed by tropicamide 0.5%
pupil size decreases more rapidly as a function of time after instillation of paremyd
what are the advantages of hydroxyampehtamine over phenylephrine?
safer for diabetics?
how does. cocaine act? what are its ocular. effects?
max effect 40-60min
why does cocaine. cause blanching of conjunctiva?
mydriasis is accompanied by vasoconstriction that causes blanching of the conj
what are. the two main clinical applications of. cocaine?
are limited due to topical ocular application causing corneal epithelial damage
1. diagnosis of horners
2. debridement of herpetic corneal ulcers due to its ability to loosen the corneal epithelium
give the five key side effects. of cocaine and its contraindications
death results from respiratory failure
corneal. epithelial irregularities, erosion
pregnancy cat c
pilopine hs gel
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