eyeballs Flashcards
uveal tract: sympathetic stim causes dilation or constriction of the pupil? what muscle?
contraction of iris dilator muscle leading to DILATION or mydriasis
mydriasis is constriction or dilatation?
dilatation
miosis is constriction or dilatation?
constriction
uveal tract: parasympathetic stim causes dilation or constriction of the pupil? what muscle?
contraction of iris sphincter muscle causing CONSTRICTION or miosis
what is a major cause of vision loss that has to do with the innermost layer of the retina?
there are no capillaries, so the choroid layer provides oxygen. detachment from the choroid compromises blood supply and is the major cause of vision loss.
how does the OCR reflex manifest cardiac
bradycardia, AV block, ventricular ectopy and asystole (rarely)
OCR can occur with any stimulation of orbital contents including lid and periosteum, but it is seen especially with ___ ____ ____
medial rectus traction
The OCR reflex is ___ in nature
trigeminovagal
OCR Reflex: where do afferent impulses originate?
orbital contents (via long and short ciliary nerves) [cn V trigeminal]
OCR Reflex: what is the efferent limb
vagus nerve to the heart
[cn X]
T/F OCR is seen during topical and general anesthesia, more during retrobulbar blocks
FALSE. it is seen less during retrobulbar blocks, although orbital injections can stimulate reflex.
OCR response is worsened by what two things
hypoxemia and hypercarbia
OCR: can pre-treat with what two drugs? consider in patients with conduction block or on BB rx
glyco or atropine
what is the formula for intraocular perfusion pressure?
MAP - IOP
If IOP is ___, blood supply and optic nerve function will be impaired
high
Once the globe is open, what can factors increasing IOP cause?
prolapse and loss of IO contents, with perm vision loss.
T/F The globe is relatively non-compliant and volume is relatively fixed except for aqueous fluid and choroid blood volume.
TRUE.
the quantity of ___ and ____ volume regulates IOP
aqueous and blood volume
what is normal IOP
10-22
IOP > ? is pathological?
25
What is the production of aqueous humor facilitated by
carbonic anhydrase
what does decreased IOP lead to?
fluid accumulation in the eye
T/F sudden increases in BP increases IOP and this has a lasting effect
FALSE. soon dissipates d/t drainage system
sudden decreases in BP<90 will drop IOP, why?
d/t loss of auto regulation.
how does 60 systolic affect IOP?
causes a 3-4 torr decrease in IOP from decreased blood flow in nl eye
what increases IOP more… increase in CVP or increase in BP?
increase in CVP
coughing, straining, breatholding, and vomiting increases IOP by _____ of drainage. IOP may increase up to ___ with coughing
obstruction. 40.
how does posture effect IOP?
same way it effects BP. sit up and it goes down.
what two factors related to the prone position have been indicated in post op vision loss?
direct pressure on the eye from compression in the prone position and lower systolic BP
decreased paco2 results in a fast drop in IOP. why?
choroidal vasoconstriction
Increase in PaCO2 results in a slow ____ in IOP
increase
a fast RR may increase IOP. why?
insufficient venous drainage
metabolic acidosis ___ IOP, while metabolic alkalosis ____ IOP
acidosis decreases the choroid vessel volume and therefore IOP.
alkalosis increases choroid vessel volume and therefore IOP
how do inhaled agents affect IOP?
decrease - because they lower BP thereby decreasing choroidal volume, relax extra ocular muscles and lower wall tension, and pupil constriction enables aqueous outflow
what is ketamines affect on IOP?
increase as it usually raises BP and doesnt relax extra ocular muscles
which induction agent is associated with myoclonus (10-60%) and may not be appropriate with an open globe?
etomidate
opioids generally ___ IOP
decrease
T/F Tracheal intubation will increase IOP if depth of anesthesia is inadequate regardless of NMR used.
TRUE
T/F non depolarizing NMR do not alter IOP.
true
curare is an exception which decreases it.
how does succs affect IOP
increases.
succs inc in IOP starts within ___ minute, increases ___ for ___ min due to prolonged contracture of extra ocular muscle
1min, 5-10,
T/F Glaucoma patient has an exaggerated response to succs
FALSE. not exaggerated or prolonged
how does acetazolamide work?
it is a carbonic anhydrase inhibitor, decreases aqueous production by inhibiting Na pump responsible for secretion of aqueous humor, decreasing IOP.
how does carbonic anhydrase chronic use effect lytes?
it depletes Na, K and bicarb, leading to metabolic acidosis
mannitol is an osmotic diuretic that is used IV intraop to drop IOP. max effect is ____min, returns to baseline after ____h
30-45. 5-6
hemorrhage is serious in which two surgeries?
orbital and oculoplastic
hemorrhage is intermediate in which three surgeries?
vitreoretinal, glaucoma, corneal transplant
T/F most providers agree it’s safe to do a cataract with patient on warfarin
TRUE
what is the most common complication of retrobulbar block
retrobulbar hemorrhage
topical applied eye drugs are absorbed at a rate ____ between subcutaneous and IV injection
intermediate
what is echothipate used for?
it is a topical anticholinesterase drug, maintains miosis to rx glaucoma
what happens with systemic absorption of echothipate
it leads to total inhibition of plasma cholinesterase. so you have prolonged muscle paralysis after succs
phenylephrine is used for what?
to dilate pupil. 2.5% causes less htn then 10%, but will aggravate BP in some
____ and ____ are cholinergic drugs used to constrict pupil. bradycardia and acute bronchospasm have been reported
pilocarpine and acetylcholine
what is timolol used for and what does systemic absorption cause?
used for glaucoma. systemic absorption can cause bradycardia, bronchospasm, and CHF exacerbation
flomax has selective alpha ____ properties. it binds to the iris dilator muscles, affecting iris dilation and complicates cataract surgery. Iris remains floppy even after ____ off therapy
antagonistic.
7-28days
if a patient has stage 3 htn (sys>180 or dias >110), reschedule until _____ of antihypertensive rx
two weeks
critical result of urea nitrogen is > ____
104
which block is utilized when complete akinesis of eyelids is desired
facial nerve block
what muscle does the facial nerve block block?
orbicular oculi
____ ____ blocks entire trunk of facial nerve , so you can expect what?
nadbath rehman
expect lower facial droop post for several hours.
injection is close to vagus and glossopharyngeal nerve.. associated with vocal cord paralysis, laryngospasm, dysphagia, and resp distress
which block is associated with proptosis and subconjunctival ecchymosis? downward displacement
RBB
arterial injection of ___ leads to high brain levels via retrograde flow in internal carotid artery. CNS excitation and seizure possibility, usually transient d/t redistribution
RBB
RBB complications: injection into optic nerve sheath leads to ____ amaurosis
contralateral (complete lack of vision)
RBB complications: injection into optic nerve sheath will manifest how neurologically ?
obtundation
RBB complications: injection into optic nerve sheath leads to resp arrest that occurs within ___ min and resolves within ____
20, hour
which block can cause a total spinal
RBB into optic nerve sheath - vascular collapse from depressant effect on the medulla
which block can cause post=op strabismus from anesthetic myotoxicitiy?
RBB
how does post-op strabismus from anesthetic myotoxicitiy present?
vertical double vision the day after surgery, worsening over 2mo.
post-op strabismus is characterized by tight ___ ___muscle
inferior rectus
how does peribulbar blockade compare to RBB
- safer
- multiple injections made around eye without entering the muscular cone
- longer onset time (9-12 min)
- less complete akinesia
- globe perf have been reported
- increased likelihood of ecchymosis
for a ruptured globe, ____ anesthesia is the only choice!!
GETA
vitroeretinal procedures — air bubble injected into the eye to tamponade the detached retina into the globe —- N20 should be d/c’d ___min before placement of sulfur hexafluoride and avoided for __ to __ days after
15min, avoid 7-10days.
____ persists for weeks so avoid n20 for one month after instillation of this agent
perfluoropropane (C3F6)
strabismus surgery is done to resection (____) and recession (____) opposite muscle
shorten, lengthen
what surgery is associated with mh
strabismus
should you use succs for a strabismus surgery?
no. 16% of these patients have a muscle disorder - dystrophic myotonia or myotonia atrophic inherited muscle wasting disease…. also associated with MH
what surgeries are associated with diabetic retinopathy, high myopia, complicated intracapsular lens extraction?
retinal detachment
what kind of anesthetic can be used for retinal detachment and virteal surgery?
RBB or general, oett(rae), or LMA
which anatomic structure is responsible for formation of aqueous humor?
ciliary body
deep inhalation and IV anesthesia ____ IOP
decrease
ketamine and hypercarbia ___ IOP
increase
what agent is used for the tx of glaucoma?
echothiophate
aqueous humor is produced by ____ and reabsorbed by ____
produced by ciliary process (posterior chamber) and reabsorbed by canal of schlemm (ant chamber)
brady with OCR is ___ likely to occur with repeated stim
less
traction of the ____ ____ muscle is associated with OCR
medial rectus
which 3 things are part of the middle layers of eye
choroid - ciliary - iris. (NOT sclera!)
orbital muscle cranial nerve VI?
lateral rectus
eye adduction muscle and CN?
medial rectus CN III
OCR afferent CN ___ which is ___, and efferent CN ___ which is ____
afferent CN V which is trigeminal, and efferent CN X which is vagus
which two drugs decrease aqueous humor production
acetazolamide and timolol
which drug promotes aqueous humor drainage
echo
*remember this drug prolongs succs and ester LA
superior rectus, inferior rectus, medial rectus, inferior oblique are CN __, lateral rectus is CN ___, and superior rectus is CN___
superior rectus, inferior rectus, medial rectus, inferior oblique are CN 3 (oculomotor)
lateral rectus is CN VI (abducens)
and superior rectus is CN IV (trochlear)
