Opthamology Flashcards
1
Q
vision loss
A
- leading cause of blindness world wide is cataracts
- DM leading cause of new cases of blindness among adults aged 20-74
- other major causes = macular degeneration, glaucoma, and diabetic retinopathy
2
Q
annulus of zinn
A
-annular ring of tissue around the optic nerve
3
Q
orbits
A
- two symmetrical bony enclosures in the front of the skull
- each contains an eyeball or globe and its associated structures
4
Q
volume of each orbit
A
30 mL
5
Q
opthalmic artery
A
- first branch of internal carotid
- passes into orbit through optic canal
- lies inferolateral to optic nerve
6
Q
visual axis
A
- aka optic axis
- imaginary line from the midpoint of the cornea to the midpoint of the retina or macula
7
Q
axial length
A
- measurement of the visual axis
- measured preoperatively to determine appropriate intraocular lens
8
Q
normal axial length
A
23-23.5 mm
9
Q
hyperopia
A
farsighted
globe is less than 22 mm long
10
Q
myopia
A
nearsighted
globe is greater than 24 mm
increased chance of puncturing globe
stretching of globe
11
Q
globe
A
- eyeball
- suspended in the antero superior part of the orbit
- contained within three layers
- large posterior segment (vitreous humor, retina, macula, and root of optic nerve
- small convex anterior segment (two chambers)
12
Q
two chambers of the anterior segment
A
- anterior chamber = immediately behind cornea, filled with aqueous humor produced by the ciliary body
- posterior chamber = contains the lens
13
Q
cranial nerves important for the eye
A
II, III, IV, V, VI, VII, X
14
Q
optic nerve
A
- CN II
- orbital portion of the optic nerve is 25-30 mm long and travels posteriorly within the muscle cone
- 4 mm diameter
- not a TRUE cranial nerve
- outgrowth of the brain (part of CNS)
- covered by meninges (pia, arachnoid, dura)
- anything injected into the nerve sheath can travel directly to the brain via CSF
- central retinal artery and vein surround the nerve
15
Q
oculomotor nerve
A
- CN III
- innervates suprior rectus, inferior rectus, inferior oblique, medial rectus, and levator (upper eyelid)
- primary motor nerve to the extraocular muscles of the orbit (branches superiorly and inferiorly)
- sends PSNS fibers to the ciliary ganglion - innervate iris sphincter muscles to cause constriction of the pupil
- SNS motor fibers control pupil dilation
16
Q
trochlear nerve
A
- CN IV
- provides motor fibers to the superior oblique muscle (to keep eye looking straight)
- only orbital cranial motor nerve that enters the orbit from outside the muscle cone
- travels in a medial direction to innervate the superior oblique muscle
17
Q
trigeminal nerve
A
- CN V
- sensory and motor components
- three divisions –> opthalmic, maxillary and mandibular
18
Q
opthalmic branch of trigeminal nerve
A
-provides sensation of pain, touch, and temperature to the cornea, ciliary body, iris, lacrimal gland, conjunctiva, nasal mucosa, eyelid, eyebrow, forehead and nose
19
Q
maxillary branch of trigeminal nerve
A
-provides senation of pain, touch and temperature to the upper lip, nasal mucosa, and scalp muscles
20
Q
three branches of opthalmic nerve
A
- lacrimal
- frontal
- nasociliary
21
Q
lacrimal nerve
A
innervates lacrimal gland
22
Q
frontal branch
A
largest branch of opthalmic nerve, further branches
23
Q
nasociliary nerve
A
sends nerve fibers medially and to the ciliary ganglion
24
Q
abducens nerve
A
- CN VI
- motor function to the lateral rectus muscle
- helps keep eyes looking straight
25
facial nerve
- CN VII
- provides motor function to the facial muscles
- upper and lower branches
- upper branch innervates the orbicular muscle, superficial facial and scalp muscles
26
vagus nerve
- CN X
- motor function to the intrinsic muscles in the larynx and heart
- major PSNS visceral innervation
- efferent pathway for the ocularcardiac reflex
27
six extraocular muscles
- surround the eye (globe)
- superior rectus (12 o'clock)
- inferior rectus (6 o'clock)
- medial rectus
- lateral rectus
- superior oblique
- inferior oblique
28
superior rectus
- moves eye upward
- supraduction
- CN III (oculomotor)
29
inferior rectus
- moves eye downard
- infraduction
- CN III (Oculomotor)
30
medial rectus
- moves eyeball nasally
- adduction
- CN III (Oculomotor)
31
lateral rectus
- moves eyeball laterally
- abduction
- CN VI (Abducens)
32
superior oblique
- rotates eyeball on horizontal axis towards nose
- intorsion, depression
- CN IV (Abducens)
33
inferior oblique
- rotates eyeball on horizontal axis temporally
- extorsion, elevation
- CN III (Oculomotor)
34
eyelid muscles
- levator muscle used for raising upper eyelids
- orbicular muscle contracts eyelid
- three divisions of muscles arranged around the eyeball (orbital, palpebral, tarsal)
- akinesia of these muscles is generally desired for ocular procedures
- contraction of these muscles can increase IOP
35
anesthesia considerations for opthalmic surgery
- changes in IOP
- CV response to traction on extraocular muscles
- absorption of topically administered drugs
- open eye surgery (GA vs local)
- succinylcholine increases IOP
- echotiopate drops
- complication of expansion of gas bubble
- post retrobulbar apnea syndrome
- laser surgery
36
IOP function
maintains normal shape and optical properties of the eye
37
normal IOP
12-20 mmHg
38
determinants of IOP
- aqueous humor dynamics --> balance between production and elimination of aqueous humor
- changes in choroidal blood volume --> vascular meshwork in posterior chamber
- rise in venous blood pressure (chronic HTN, not acute changes in BP)
- extraocular muscle tone
39
aqueous humor
- thin, watery fluid that fills the space in the anterior chamber between the cornea and iris
- nourishes the cornea and lens
- gives the front of the eye its form and shape
- continually produced by ciliary body which lies just behind the iris
- drains out of the eye via the trabecular meshwork into the aqueous veins and eventually into the veins of the orbit
40
what increases IOP
- blinking (5 mmHg increase)
- squinting (26 mmHg increase)
- CV/respiratory variables (CVP, ABP, PaCO2)
- laryngoscopy and intubation
- external pressure/positioning
- succinylcholine
- topical anticholinergics
41
what decreases IOP
- volatile anesthetics
- IV anesthetics (except ketamine)
- NDMR
- benzos
- narcotics
42
succinylcholine and IOP
- increases IOP by 5-10 mmHg for 5-10 min
- mechanism is unlcear
- may be result of prolonged contraction of extraocular muscles
- no consistent method to prevent increase
43
oculocardiac reflex efferent and afferent
-efferent = trigeminal (CN V)
-afferent = vagus (CN X)
why it is called the "five and dime reflex"
44
why does the oculocardiac reflex occur?
pain, pressure or manipulation of the eyeball
| COMMON CAUSE = traction of medial rectus muscle
45
symptoms of oculocardiac reflex
- cardiac dysrhythmias (bradycardia, sinus arrest, v-fib, AV block, ventricular ectopy) and negative inotropy
- transient cardiac arrest occurs in 1:2200 strabismus surgeries
46
most common surgery for oculocardiac reflex
- pediatric strabismus surgery
- transient cardiac arrest occurs in 1:2200 strabismus surgeries
- attenuated by pretreatment with anticholinergics
47
treatment of oculocardiac reflex
- stop stimulus
- administer atropine/glyco
- infiltration of LA to the medial rectus muscle
48
surgery for detached retina
- small gas bubble injected into posterior chamber to hold retina in place
- sulfur hexafluoride most commonly used
49
sulfur hexafluoride
- inert poorly diffusible gas
- much less soluble in blood than nitrogen and N2O
- DOA is 10 days
- nitrogen from inhaled air enters bubble faster than SH can diffuse into blood, allowing the bubble to expand (doubles in 24 hours)
- inhaled 70% N2O can triple the size of the bubble and quickly increase IOP
- can be reversed if N2O discontinued within 18 minutes, the pressure changes can lead to negative outcomes
- discontinue N2O 20 min prior to injection to allow for washout
- avoid N2O for 10 days after SH (5 days if injected air)
50
opthalmic mydriatics
- atropine/scopolamine - anticholinergic; central cholinergic syndrome can occur or disorientation
- epi - sympathetic agonist; tachycardia, arrhythmias, HTN, HA
- phenylephrine - alpha agonist; HTN, arrhythmias, HA, reflex bradycardia
- cyclopentolate - synthetic anticholinergic; disorientation, psychosis, seizures
51
pilocarpine
- muscarinic alkaloid
| - miosis, redness, irritation
52
carbachol
- synthetic carbamyl ester of choline
| - used if not responsive to pilocarpine
53
physostigmine
- indirect acting anticholinesterase
| - miosis
54
echothiopate
- indirect acting organophosphorus cholinesterase inhibitor
- miosis
- used for treatment of glaucoma
- irreversible cholinesterase inhibitor
- systemic absorption leads to decreased plasma cholinesterase activity
- lasts 3-6 weeks after d/c
- succ will be prolonged 20-30 minutes
- may also prolong mivacurium and ester linked LAs
55
timolol
- potent non-selective beta blocker
| - bradycardia, asthma, CHF
56
acetylcholine
- cholinergic agonist
| - miosis, bradycardia, bronchospasm, hypotension
57
acetazolamide (diamox)
- use this a lot
- carbonic anhydrase inhibitor
- reduces secretion of aqueous from ciliary body, mild diuretic, hypokalemia, acidosis, hematuria, paresthesia, gastric distress, flaccid paralysis, seizures
- avoid with renal/hepatic disease
- avoid in those with allergy to sulfa abx
58
local anesthetics
- topical local anesthesia often used for optho surgery
- most often placed by surgeon
- toxicity is rare
- topical agents used = tetracaine, proparacaine, bupivacaine, lidocaine, cocaine
- blocks = bupivacaine, mepivacaine, lidocaine
59
how do topical eye medications work?
enter bloodstream through the outer eye membrane and lacrimal apparatus
60
measures to reduce the amount of med that enters the bloodstream
- close eyes for 60 seconds after drops instilled to encourage absorption by eye
- avoid blinking
- block tear outflow canal (place index finger over medial canthus)
61
topical/intraocular anesthesia
- cataract and vitreoretinal surgeries are most frequently performed intraocular procedures
- topical anesthesia for cataract is effective in providing adequate analgesia
- intraocular anesthesia with 1% lidocaine
62
ocular regional anesthesia
- most common and effective way to consistently produce analgesia and akinesia of the eye and eyelids
- ocular local anesthesia - peribulbar block and retrobulbar block
- anesthetize multiple cranial nerves (III, IV, V, VI, VII)
- orbital epidural space
- facial nerve block
63
peribulbar block (PBB)
- injection of LA outside the muscle cone
- provides analgesia and akinesia of the eye
- relatively low complication rate
- many variations on technique
- patient needs to look straight ahead (avoid vasculature and optic nerve)
- use a dull, short beveled 25-27G 22 mm needle
- insert needle in lateral aspect of inferotemporal quadrant and superiornasal
- do NOT insert beyond 25 mm or pierce muscle cone
- aspirate before slow injection
- 6 mL of LA
- lido + bupi (+/- epi)
64
PBB disadvantages compared to RBB
- large volumes injected (6-8 mL)
- may increase IOP
- slower onset of action (5-10 min)
- possible perforation of globe
- vertical diplopia (myotoxicity from LA)
65
three injections of PBB
- superior injection
- medial canthus
- inferotemporal injection
66
retrobulbar block (RBB)
- injection of LA inside the muscle cone
- provides analgesia and akinesia of eye
- higher complication rate than PBB
- insert 25G needle through lower lid at the junction of the lateral third and medial 2/3 of the inferior orbital edge
- advance 25-35 mm toward apex of orbit (19-31 mm safest)
- ASPIRATE and inject 2-5 mL of LA
- lido and bupi most common
67
complications of RBB
- complications occur in 1:5000 blocks
- trauma to optic nerve
- vision loss
- retrobulbar hemorrhage
- globe perforation
- oculocardiac reflex
- brainstem anesthesia (injection into optic nerve sheath)
- IV or intra-arterial injection
- seizure
- respiratory or cardiac arrest
- usually occur within 15 min after block
68
RBB contraindications
- bleeding disorders
- anticoagulation
- extreme myopia
- open eye injury
69
sub-tenon's (episcleral) block
- LA placed into potential space between Tenon's capsule and the sclera
- inferonasal conjunctival fornix most commonly used
- direct needle posteriorly following curve of globe
- superficial injection allows LA to spread circularly around scleral portion of globe
- larger volume allows spread to extraocular muscle sheaths
- deep injection - posterior intra and extra conal spaces (2-5 mL) is most common
70
facial nerve block
- periocular branches of the facial nerve
| - done to prevent excessive blinking during surgery
71
percentage of closed claims for optho against anesthesia
- 30% of eye injury claims due to patient movement during opthalmic surgery
- blindness was outcome in all cases
72
preop considerations for opthalmic surgery
- most procedures can be performed under regional and sedation
- same standard of care
- NPO status
73
indications for GA in optho
- pediatric patient
- patient lack of cooperation
- severe claustrophobia
- inability to communicate
- inability to lie flat
- open-eye injuries
- procedures with duration greater than 2 hours
74
intraop management sedation for optho
- short acting agents because usually short procedures
- prevent cardiac or respiratory side effects
- meds = fentanyl, alfentanil, remi, midaz, prop, dexmedetomidine
75
optho procedures intraop management
- unnecessary to maintain sedation if block is adequate
- OR turned 90-180 degrees
- standard monitors
- oculocardiac reflex
- temperature
- fluids
- light GA for little stimulation
- hypotension
- oxygen and cautery
- risk of corneal abraision, retinal artery occlusion
76
post-op management of optho procedures
- PONV very common
- postop eye pain unusual (usually means either a corneal abrasion or acute intraocular HTN that needs to be treated with mannitol or diamox)
- elderly patients with a history of MI are at increased risk for ischemic events even under LA (consider periop beta-blockers)
77
strabismus surgery
- ocular misalignment
- most common opthalmic condition requiring surgical repair in children
- intervention should occur before 4 months to allow normal stereoscopic visual development
- surgery lengthens/shortens ocular muscles to straighten the eyes and allow binocular vision
- 30-60 min
- GA
- minimal EBL
- table turned away from you
78
strabismus side effects
- ocularcardiac reflex (increased PaCO2 shown to decrease this during surgery; stop stim, admin anticholinergics, LA infiltration)
- increased risk of MH
- associated with underlying myopathy so higher risk of MH (avoid triggers and be vigilant)
79
strabismus and PONV
- 48-85% incidence
- ocular emetic reflex
- possible disruption of surgical repair
- prevention includes hydration, minimize opioids, avoid N2O, propofol, LA infiltration near extraocular muscle, antiemetics (zofran and decadron)
80
penetrating eye injury anesthetic considerations
- full stomach precautions
- aspiration risk
- prevent increase in IOP (succ increases within 1 min, peaks at 9 mmHg increase after 6 min; avoid coughing)
- open globe = succ or no succ; laryngoscopy increases IOP so be mindful, consider NDMR for RSI
81
open globe + full stomach
- emergency surgery with GA
- dos and dont's to prevent aspiration
- do not attempt to evacuate contents using NGT preop
- do administer metoclopramide, H2 antagonists, non-particulate antacid prior to induction
- do NOT attempt regional
- do attempt RSI using cric pressure and avoid PPV
- DO extubate awake, spontaneously breathing, head turned to side
82
things to prevent increase in IOP
- avoid direct pressure on eye
- avoid trendelenburg position
- avoid regional
- avoid increase in CVP
- avoid drugs that increase IOP
- avoid agitation in young children
83
anesthesia complications in optho
- retrobulbar hemorrhage
- globe puncture
- optic nerve sheath trauma
- intravascular injection
- ocular ischemia
- extra-ocular muscle palsy and ptosis
- facial nerve blocks
- oculocardiac reflex
- corneal abrasion
- central retinal artery occlusion
84
retrobulbar hemorrhage
- results from trauma to orbital vessel
- moves eyeball forward
- venous hemorrhages have slow onset, arterial has rapid onset
- lateral canthotomy may be indicated if hemorrhage is not resolved by digital pressure
85
lateral canthotomy
- increase orbital space by cutting lateral canthus
- reduces orbital pressure that results from hemorrhage
- place hemostat in temporal direction along lateral canthus 4-6 mm and clamp hemostat
- use scissors to incise the crush marks left by hemostat
- control local bleeding
86
globe puncture
- sharp and dull needles both reported to have penetrated eye during injection
- globe can burst apart from IOP caused by injection
- risks = miopic eye, scleral thinning, scleral buckling, bulging of sclera
- prevent = avoid supranasal position of gaze, direct needle away from axis of globe during insertion, insert needle slowly with bevel toward globe, never forecully inject LA, use modified techniques
- symptoms = increased resistance to injection, dilation/paralysis of pupil, increased IOP, hemorrhage
87
optic nerve sheath trauma
- optic sheath surrounds optic nerve
- outer sheath = dura mater
- inner sheath = arachnoid and pia mater
- subarachnoid space contains CSF and is continuous with optic chiasm
- dura splits into two layers at optic foramen - inner layer forms dural covering of optic nerve and forms orbital epidural space
- observe contralateral pupil before block, if contralateral pupil constricted --> dilated after block, assume subarachnoid/subdural injection and prepare for respiratory arrest
88
ocular ischemia
- retinal vascular occlusion or thombosis has been reported after ocular blocks
- decreased pulsatile ocular blood flow after blocks
- optic nerve atrophy reported after regional or GA
- transient symptoms of optic nerve injury include contralateral amaurosis or respiratory arrest; vascular occlusion/thrombosis which may lead to loss of vision
89
extraocular muscle palsy and ptosis
- inferior muscle palsy reported after retrobulbar anesthesia
- symptom = persistent vertical diplopia
- surgical intervention may be indicated
- prevention = avoid needle contact with extraocular muscles, avoid deep orbital penetration, avoid angling needle toward visual axis of globe
- myotoxocity of LA may cause postop diplopia and or ptosis
90
facial nerve block
- discomfort from block of CN VII
- bell's palsy may occur secondary to direct nerve trauma
- dysphagia, hoarseness, coughing and respiratory distress reported due to paresis of the vagus, glossopharyngeal and spinal accessory nerves
- prevention = avoid large volume LA, avoid nadbath technique in certain patients, seated/lateral position to protect airway, intubate if airway concerns
