Mydriatics and Cycloplegics Flashcards
What are catecholamines?
hormones including dopamine, epinephrine, and norepinephrine = produced from tyrosine in post-ganglionic fibers in ANS and adrenal medulla
What are the 2 enzymes for catecholamine metabolism?
COMT and MAO
What is cycloplegia?
paralysis of ciliary body musculature responsible for accommodation
What is anaphylaxis?
an acute, systemic allergic hypersensitivity reaction to a previously sensitized allergen
What causes histamine release, bronchoconstriction, vasodilation, and swelling during anaphylaxis?
IgE in bloodstream reacting with the antigen
What are the treatments for anaphylaxis?
O2, IV steriods, airway management (intubation) and EpiPen
Why is an Epipen effective for anaphylaxis reactions?
Epinephrine will counteract the anaphylaxis symptoms and restore normal BP and prevent shock
What conditions should you use caution in when administering an EpiPen?
heart disease, high BP, Parkinson’s disease, diabetes, and thyroid disorders
What regulates the fight or flight response?
sympathetic or adrenergic branch of ANS
What regulates the rest and digest response?
parasympathetic or cholinergic branch of ANS
What are the neurotransmitters in the sympathetic system?
epinephrine and norepinephrine
what is the neurotransmitter of the parasympathetic system?
acetylcholine
What is the receptor type for ganglia within the sympathetic system? (post-ganglionic neurons)
nicotinic receptors
What is the receptor type(s) for sympathetic adrenergic system?
alpha and beta
what is the receptor type for the sympathetic cholinergic system at the terminal organs?
muscarinic receptors
what is the receptor type for parasympathetic cholinergic system at the terminal organ?
muscarinic receptors
where are alpha 2 receptors primarily located?
pre-synaptic and stimulation causes inhibition of signal propagation
What are 2 things that occur with stimulation of alpha 2?
decreased insulin release and decreased aqueous production
What are 2 things that occur with stimulation of alpha 1?
vasoconstriction, mydriasis
what are 5 things that occur with stimulation of beta 2?
vasodilation, bronchodilation, glucogenolysis, increased insulin release, and relaxation of ciliary body with increased aqueous production
what occurs with beta 1 stimulation?
increased cardiac contractility and conduction
what is alpha 1 selective for?
NE>E
what is alpha 2 selective for?
E greater than or equal to NE
what is beta 1 selective for?
E=NE
what is beta 2 selective for?
E
What is the backbone of catecholamines?
tyrosine
what is tyrosine converted to once inside a pre-synaptic nerve terminal in sympathetic system?
converted to dopamine
what happens to dopamine after being converted from tyrosine?
placed in vesicles (stable and remains stored until needed) –> converts to NE when needed
What are the steps following a nerve impulse in the sympathetic system?
Ca++ uptake is facilitated and enters terminal –> with elevated Ca levels = degranulation of vesicles into synaptic cleft
what happens if NE acts as bio-feedback and stimulates an alpha 2 receptor?
interferes with Ca++ ability to cause degranulation and stops NE release
Where are MAO and COMT located to help metabolize NE?
MAO is in pre-synaptic terminal and COMT is in post-synaptic terminal
what happens to NE with cocaine and amphetamines?
blocks NE in synaptic cleft
what are the 5 ocular adrenergic effects (fight or flight)?
mydriasis, increased IP aperature, modulate aqueous production, modulate vascular tone, receptors in trabeculum and schlemms canal suppress accommodation
what are some examples of cases with reduced sensitivity for dilation?
age-related miosis, unstable diabetes, post-op pupils, posterior synechiae, dark iris, pseudoexfoliation syndrome
what is an example of a case with increased sensitivity to dilation?
down syndrome
what are some cases you need to use caution before dilation?
homocystinuria and marfan’s syndrome, pregnancy, pigmentary or exfoliative glaucoma
what are some examples of contraindications for dilating?
iris supported IOL, subluxated lens or IOL, extremely narrow angle, angle closure history w/o PI
how soon will a patient have an iatrogenic angle closure after dilation?
4-8 hours post instillation
what occurs to the ciliary body with cycloplegia?
prevents the ciliary body from contracting = disables accommodative function
what are some examples of times you would want to use cycloplegia?
strabismus (esotropia), pseudomyopia/accommodative spasm, latent hyperopia, anisometropia, amblyopia, malingerers, unexplained refractive error or un-responsive patients
what are 2 sympathetic mydriatics?
phenylephrine and hydroxyamphetamine (PAREMYD)
what is the activity of phenylephrine?
alpha 1 selectivity and some indirect effects via NE release
What are some actions of phenylephrine?
mydriasis (45-60min), conjunctival blanching (vasoconstriction), mild accommodation suppression (2D), lid retraction, IOP reduction **fight or flight actions
What are 4 special indications that Phenylephrine can be used for (other than mydriasis)?
posterior synechiae breakage, pre-Lasik vasoconstriction, inhibition of iris cysts (caused by echothiophate), horner’s evaluation
How can phenylephrine help diagnose Horner’s syndrome?
use 1% - it will dilate the pupil with post-ganglionic sympathetic denervation and cause no/minimal dilation in the normal eye
What are some adverse effects of phenylephrine?
photophobia/glare, allergic dermatoconjunctivitis, rebound miosis, anterior chamber pigment liberation, hypertension/bradycardia
What is rebound myosis?
patient responds to agent with mydriasis but when effect wears off the miotic response is bigger (pupil is smaller than normal)
What are some contraindications for phenylephrine?
avoid 10% in neonates/elderly, history of CVD/MI, DM1, aneurysm, arteriosclerosis, hypotension, drugs: atropine, TCAD, MAOI, reserpine, guanethidine, methyldopa
What is hydroxyamphetamine used for?
mydriasis without suppressing accommodation - can be used to differentiate between pre-ganglionic and post-ganglionic sympathetic denervations (PAREYMD can too)
What does hydroxyamphetamine act on?
indirect acting - promotes NE release from nerve terminals (blocks uptake of NE and keeps it in synaptic cleft)
What is PAREMYD?
1% hydroxyamphetamine and 0.25% Tropicamide
What are 3 benefits of PAREMYD?
mydriasis independent of age or pigmentation, faster recovery then phenylephrine/tropicamide (better for shallow angles), no benefit to anesthetic before use
What is different about the adverse effects of PAREMYD vs. Phenylephrine?
leads to tachycardia instead of bradycardia
Which types of patients is PAREMYD safer in vs. phenylephrine?
diabetics, hypotension, chemical sympathectomy agents
Are the parasympathetic receptors inhibitory or stimulatory?
all are stimulatory (sympathetic receptors are both)
What is the M1 receptor associated with?
memory
Which parasympathetic receptor is better at miosis and ciliary body contraction/increased aqueous production?
M3
Which parasympathetic receptor is responsible for salivary glands and vasodilation?
M3
Which parasympathetic receptor is better at cardiac contractility and conduction?
M2
Which parasympathetic receptor is responsible for emesis?
M3
Which parasympathetic receptor is responsible for bronchoconstriction and secretion?
M2 = M3
What 2 things does Acetylcholine break down into? (2 esters)
acetate and choline (broken down by esterases = AChE)
What happens when choline enters a nerve terminal?
choline adds with acetyl-CoA to make ACh and placed into vesicles
What happens in the parasympathetic system when Ca++ enters a nerve terminal?
triggers degranulation and the ACh vesicles are released into the synaptic cleft where AChE breaks it down into acetate + choline
Name 6 anticholinergic agents?
atropine, scopolamine, homatropine, tropicamide, cyclopentolate and cyclomydril
Which parasympathetic receptors does Atropine use?
non-selective M receptors
which anticholinergic agent is selective for M4 only?
Tropicamide
what is cyclomydril made of?
0.2% cyclopentolate + 1% phenylephrine
What is atropine used for?
cycloplegia, severe uveitis, amblyopia, ciliary body spasm, synechiae, lens advancement, vessel permeability, myopic progression
what is scopolamine used for?
travel sickness (emesis) - pronounced CNS effects
what is homatropine used for?
moderate uveitis, corneal abrasions, mydriasis
what is cyclopentolate used for?
cycloplegia, moderate uveitis, corneal abrasions
delayed/sustained effects in dark pigment iris (less flushing and dryness than atropine)
what is tropicamide used for?
cycloplegia, mydriasis, mild uveitis
What are 3 ocular adverse effects for anticholinergics?
increased IOP, angle closure risk and allergy
What are the ABCDs (systemic) adverse effects of anticholinergics?
Anorexia, blue, constipation/confusion, dryness, sedation/stasis of urine
What are 2 adverse effects for anticholinergics in the CNS (medulla)?
decreased Parkinson tremor and decreased heart rate
what are some contraindications for anticholinergics?
classic antihistamines, TCADs, anti-psychotics, Down syndrome, albinism, cerebral palsy, narrow angle, iris supported IOL, spastic paralysis, OAG, ACG
What combination of drugs gives the best mydriasis outcome?
0.25% tropicamide + 1% PAREMYD
what is the safest dilation drop to use?
tropicamide (only lasts about 6 hours = shortest duration)
which drop do you administer 1 drop initially then another 15-25 min later?
cyclopentolate
which cycloplegic drop lasts the longest?
Atropine (7-12 days)
