opthamologic Flashcards
1
Q
eye globe lies in 2
A
orbits
2
Q
most frequent procedure performed worldwide?
A
cataract
3
Q
2 symmetrical bony enclosures on skull contain:
A
- globes
- pyramidal cavity with base in front and apex behind
4
Q
each orbit has a volume of approximately
A
30 mL
5
Q
optic foramen/canal >
A
optic nerve & opthalmic artery & sympathetic nerves of carotid plexus
6
Q
the average adult globe diameter is
A
23.5 mm (about an inch)
7
Q
cornea
A
highly vascular and transparent, permits, light passing
8
Q
conjunctiva
A
- outer surface
- tendons of rectus muscles insert (responsible for refraction of light entering eye)
9
Q
sclera
A
fibrous, outer layer, protective, maintains shape
10
Q
iris
A
- colored part
- contains dilator and sphincter muscle fibers that control the central aperture
11
Q
pupil
A
controls light passing into eye
12
Q
parasympathetic stimulation originating from the cranial nerve III the..
A
nucleus contracts iris sphincter fibers, causing pupillary constriction or miosis
13
Q
sympathetic fibers traveling with the ophthalmic division of
A
CN V stimulates iris dilator fibers, dilating pupil
14
Q
most common injury after GA
A
corneal abrasion
15
Q
how does corneal abrasion occur?
A
- drying or trauma (mask injury/pt. rubbing their eyes)
16
Q
how to prevent corneal abrasion
A
tape eyes
17
Q
what can happen during eye surgery that can cause injury?
A
movement or bucking during eye surgery common mechanism of injury
18
Q
positioning
A
> CRAO from prolonged pressure (prone position)
19
Q
chemical injury
A
from spilling of cleaning solutions (flush with saline)
20
Q
posterior segment
A
- vitreous humor, retina, macula, root of optic nerve
21
Q
retina
A
The neurosensory membrane converts light that enters eye into electrical signals the optic nerve sends to the brian to create images
22
Q
macula
A
oval pigmented area in center of retina/central, high-acuity vision
23
Q
anterior segment
A
2 chambers
24
Q
anterior chamber
A
behind cornea filled with aqueous humor or vitreous humor
25
posterior chamber: lens
refracts rays of light passing through the cornea and pupil to focus image on retina
26
what separates the chambers?
iris and communicate via pupil
27
how many extraocular muscles? how many rectus and oblique muscles?
4 rectus msucles
2 oblique muscles
28
the four rectus muscles delineate the __ __
retrobulbar cone
29
name 4 rectus muscles
superior, inferior, lateral, medial rectus
30
name 2 oblique muscles
superior and inferior
31
the cavity of the orbit has a __ pyramid shape, with a __ apex, and a __ corresponding to the anterior opening
truncated; posterior; base
32
sensory innervation to orbit and globe
- frontal and nasociliary branches of the ophthalmic nerve (first branch of trigeminal nerve V)
- part of the floor of orbit supplied by infraorbital and maxillary nerve (second branch of trigeminal nerve)
- the optic nerve CN II carries the sensory info from the retina
33
trigeminal nerve has 3 divisions
ophthalmic, maxillary, mandibular
34
motor innervation
CN IV, VI, III
35
trochlear IV
supplies superior oblique muscles
36
abducens VI
supplies lateral rectus
37
Branch of CN III
supplies motor root to ciliary ganglion > sphincter of pupil and ciliary muscle
38
oculomotor III
supplies extraocular muscles
39
Superior recuts
- innervation
- function
- CN III
- elevation
40
Inferior recuts
- innervation
- function
- CN III
- depression
41
Medial recuts
- innervation
- function
- CN III
- adduction
42
Inferior oblique
- innervation
- function
- CN III
- elevation, abduction and medial rotation (intorsion)
43
Superior oblique
- innervation
- function
- IV trochlear
- depression, adduction, and external rotation (extortion)
44
zygomatic branch of facial nerve:
- upper branch > frontalis and upper lid
- lower branch > orbicularis of lower lid
45
lateral rectus
- innervation
- function
- VI abducens
- abduction
46
oculocardiac reflex aka
trigeminovagal relfex
47
traction of the extraocular muscles or __ on the globe causes __, junctional rhythm, AV block, ectopic beats, asystole, __ __
pressure; bradycardia; ventricular tachycardia
48
afferent limb:
orbital content > ophthalmic division (V1) of trigeminal nerve > sensory nucleus trigeminal nerve
49
efferent limb
> vagus nerve through connections to the visceral motor nucleus in reticular formation > decreases output from SA node > bradycardia
50
trigeminal nerve divisions
V1: opthalmic
V2: maxillary
V3: mandibular
51
oculocardiac reflex S/S
hypoxia, hypercarbia, light anesthesia, acidosis increase the incidence and severity
52
oculocardiac reflex triggering stimuli
- traction on extraocular muscles (especially medial rectus)
- direct pressure on globe
- ocular manipulation
- ocular pain
- manipulation of orbital apex after enucleation
- eye blocks - retrobulbar block
- ocular trauma
- (may occur during regional or general)
53
oculocardiac reflex treatment
- ask the surgeon to stop manipulation
- make sure the patient is deep enough and properly ventilated
- if bradycardia persists, give atropine 0.02 mg/kg increments (or glycopyrrolate 0.2-0.4 mg IV)
- if it persists, may need to infiltrate rectus muscle with LA
- reflex does fatigue with repeated ocular stimulation
54
bradycardia d/t
a range of stimuli in or around the orbit, such as traction on the extraocular muscles, pressure on the globe, retrobulbar block, ocular trauma or pressure on residual tissues after enucleation
55
causes other arrhythmias
including vtach and rarely asystole
56
the relevant neuropathways are branches of the trigeminal nerve (afferent) and vagus nerve (efferent)
while mainly associated with stimulation of the ophthalmic nerve, it occur with any branch of the trigeminal nerve
57
incidence is highest in
children
up to 90% without pre-treatment with atropine
58
prophylaxis treatment in children
- atropine 0.02 mg/kg
- glycopyrrolate 0.01 mg/kg prior to surgery is often practiced
59
T/F IM atropine is not useful d/t delayed onset
true
60
regional blocks afferent limb
may reduce risk
61
treatment of bradycardia includes
- removal of stimulus
- asking the surgeon to stop the stimulation
- initiation of IV anticholinergics (exp. 5-10 mcg/kg of atropine or glycopyrrolate 2.5-5 mcg/kg), and checking the depth of anesthesia (where GA is used)
62
normal IOP is
10-21.7 mm Hg
63
IOP is tissue pressure of
intraocular contents
64
IOP is maintained at equilibrium when
there is a balance between aqueous humor production and drainage of fluid through episcleral veins
65
IOP > __ mm Hg = abnormal
22
66
elevated IOP
prolonged IOP > retinal ischemia or hemorrhage > loss of optic nerve function and permanent vision loss
67
what increases the IOP
- impairment of aqueous drainage
- increase in choroidal blood volume
- glaucoma
- compression of the eye
- laryngoscopy/emergence
- hypoxia/hypercapnia
- HTN
- coughing, straining, vomitting (30-40 mm Hg)
- ocular blocks (5-10 mm Hg)
- cardiac contraction (1-2 mm Hg)
- positions - supine, prone, trendelenburg
- blinking (5-10 mm Hg)
- forceful lid squeeze (70 mm Hg)
68
PaCO2 increase (hypoventilation) effect on IOP
increase
69
PaCO2 decrease (hyperventilation) effect on IOP
decrease
70
PaO2 decrease effect on IOP
increase
71
acetylcholine
- cholinergic agent
- miosis
- bradycardia, bronchospasm, hypotension
72
Acetazolamide (PO, IV, IM)
- carbonic anhydrase inhibitor
- decrease IOP, glaucoma
- confusion, drowsiness, hypokalemia, hyponatremia, metabolic acidosis, abnormal hepatic function tests, polyuria, renal failure
73
- inhibits neurovascularization
- conjunctival hemorrhage, eye pain, endophthalmitis, uveitis, stroke (in high-risk patients)
74
ophthalmic medications
- topical eye drops are absorbed by vessels in the conjunctival sac and nasolacrimal duct mucosa at a rate between IV & SQ injection
- 1 drop (1/20 mL) of 10% phenylephrine contains 5 mg of drug
- echothiophate (phospholine iodide) prolongs action of succ good thing we done use it much anymore
- timolol causes bradycardia
75
conditions that could influence anesthetic managment
- dementia
- deafness
- restless leg syndrome
- OSA
- tremors
- claustrophobia
76
If patient cannot lie flat d/t pulmonary issues >
GA
anticoagulation is okay 👍🏼
77
during ocular block
- IV sedation
- NO movement during block
- challenge: deep but not too deep; awake but not talking
78
during the procedure for ocular block
- sedation may be difficult (minimize to reduce risk of side effects)
- often need cooperation
- avoid over sedation/airway obstruction
- heavy sedation is not a substitute for inadequate analgesia !!
- cataracts under topical (no ocular block)
- turn off O2 with cautery or during laser
- goal often < 30% FiO2 - monitor oxygenation and ventilation
- ocular blocks will last 2-3 hrs
79
when should I use GA?
- long duration
- patient fears
- pediatrics
- cognitive impairment
- hearing loss
80
multimodal analgesia
- NSAIDS
- acetaminophen
- gabapentin
81
postoperative: pain?
- cataracts - no
- corneal surgeries, enucleations, and ocular muscle surgery - YES
82
things to consider with GA
- antiemetics
- smooth induction/intubation
- avoid oculocardiac reflex; know how to treat it if it happens
- motionless field
- smooth extubation
- consider LMA
- requires OET: vitrectomy, trauma to eye, vitreoretinal procedures
- airway will be away from you
- nitrous oxide??
83
Treat PONV
be suspicious of PONV
84
GA for open-eye surgery
- smooth IV induction (no coughing bucking) > greater especially with open globe
- RSI with full stomach
- difficult airway > consult opthalmologist > weigh risk vs. benefit of techniques > consider careful awake FOB
- extubation > consider IV lidocaine and adequate narcotic
- consider deep extubation with no aspiration risk
85
open eye injury, treatment goals
- avoid elevated IOP at induction and extubation
- prevent aspiration (usually traumatic with full stomach)
- RA may increase IOP with injection of LA (avoid)
- GA safest
- avoid trendelenburg
- use care with mask ventilation (external pressure on eye
86
what used to be the gold standard type of RA block for eye surgeries?
retrobulbar block
87
what did close claim analysis find that was an identifiable cause of eye injury claims?
patient moving during ophthalmic surgery and needle trauma r/t orbital block
88
T/F RA is not standard for ophthalmic procedures: cataracts, glaucoma, cornea, vitreoretinal surgeries
FALSE
89
what has a higher risk of complications? retrobulbar block or peribulbar block?
retrobulbar block
90
uses: retrobulbar block & peribulbar block
- corneal
- anterior chamber
- lens procedures
91
what block is outside the cone of the eye?
peribulbar block
92
pharmacological choice: retrobulbar block & peribulbar block
- retrobulbar: 1.5 - 5 mL LA
- peribulbar: 4 - 6 mL LA (up to 12 mL)
93
position: retrobulbar block & peribulbar block
supine
maintain "primary gaze"
94
sedation: retrobulbar block & peribulbar block
+/- propofol
95
where is the LA injected into in a retrobulbar block?
inside the muscular cone
96
what does the retrobulbar block aim to block?
ciliary nerves, the ciliary ganglion, & CN (II?), III, IV, and VI
97
does the retrobulbar block, block the facial nerve? CN VII
no, may need a facial nerve block to prevent blinking
98
what orbital muscle is NOT in the muscular cone ?
superior oblique, so may not have total akinesia
99
a successful retrobulbar block is accompanied by
anesthesia, akinesia (not total), and abolishment of the oculocephalic reflex (exp. blocked eye does not move during head-turning)
100
position for retrobulbar block
- sitting or supine
- with or without sedation (commonly performed with brief period of deep sedation)
- patient keeps eye neutral
101
needle insertion for retrobulbar block
- inserted perpendicularly at the junction of the lateral third and medial two-thirds of the inferior orbital rim aimed cephalad and medial
- walked a depth of 25-35 mm
- aspirate
- inject 1.5 - 5 mL
102
forceful injection of LA into the __ __ causes retrograde blood flow toward the brain and may result in an instantaneous __
ophthalmic artery; seizure
103
complications of retrobulbar block
- retrobulbar hemorrhage
- perforation of the globe
- optic nerve injury
- intravascular injection with resultant convulsions
- oculocardiac reflex
- trigeminal nerve block
- respiratory arrest
- acute neurogenic pulmonary edema
104
postretrobulbar block apnea syndrome
injection of LA into the optic nerve sheath with spread to the CSF
105
postretrobulbar block apnea syndrome S/S
CNS exposed to high concentrations of LA leading to mental status changes that may include unconsciousness, apnea occurs within 20 mins and resolves in an hour
106
postretrobulbar block apnea syndrome treatment
- supportive
- positive pressure ventilation: to prevent bradycardia, hypoxia, and cardiac arrest
107
contraindications of retrobulbar block
- age < 15
- procedures lasting longer than 90-120 mins
- uncontrolled cough or tremors
- disorientation or mental impairment
- excessive anxiety or claustrophobia
- language barrier or deafness
- coagulopathies
- perforated globe
108
where do you inject peribulbar block?
extraconal space
needle does not penetrate cone formed by extraocular muscles
109
how much volume is given of LA in a peribulbar block?
4 - 12 mL
110
position for peribulbar block
supine
111
what does a peribulbar block, block?
ciliary nerves, CN III & IV, but does NOT block the optic nerve
112
needle insertion for peribulbar block
2 injection sites
- 1st inferior and temporal regions
- same location as retrobulbar block but smaller cephalad and medial adjustment
- NO POP- needle not entering the muscle cone
- 2nd between medial third and lateral two-thirds of orbital roof edge
- aspirate and inject 4 -12 mL
113
advantages of peribulbar block
- there is less potential for intraocular or intradural injection since LA is deposited outside the muscular cone
- less risk of globe perforation
- less risk of intravascular injection
- the risk of hemorrhage decreased
- risk of injury to optic nerve decreased
- no need for additional lid block
- technically easier to place
114
Disadvantages of peribulbar block
- more difficult to get a complete, dense block
- slower onset
- risk of ecchymosis
115
superficial sub-tenon injection
- analgesia of globe with low volumes (3-5 mL)
- akinesia with high volumes (8-11 mL)
can be superficial or deep injection depending on goal
116
sub tenon anesthesia injection is where?
episcleral space
potential space between tenons capsule and sclera
117
needle insertion for sub-tenon anesthesia
any quadrant of globe
most common - inferonasal conjunctival fornix
118
complicaitons with sub-tenon blocks
are less than with retrobulbar and peribulbar blocks
- globe perforation, hemorrhage, cellulitis, permanent visual loss, and LA spread into the CSF have been resported
119
S/S of globe perforation
ocular pain, intraocular hemorrhage, restlessness
120
mechanism of complication of globe perforation
direct trauma: myopic eye, posterior staphyloma, repeated injections
121
S/S retrobulbar hemorrhage
subconjunctival or eyelid ecchymosis, increasing ptosis pain, and/or increased IOP
122
mechanism of complication of retrobulbar hemorrhage
direct trauma (artery or vein)
123
S/S optic nerve damage
visual loss, possible early optic disc swelling, late optic disc pallor
124
S/S intra-arterial injection
cardiopulmonary arrest & convulsions
125
mechanism of complication of optic nerve damage
direct injury to nerve or blood vessels, vascular occlusion
126
mechanism of complication for intra-arterial injection
retrograde flow to ICA and access to midbrain structures
127
S/S optic nerve sheath injection
brainstem anesthesia: agitation, ptosis, mydriasis dysphagia, dizziness, confusion, contralateral ophthalmoplegia, loss of consciousness, respiratory depression/arrest, cardiac arrest
128
mechanism of complication for optic nerve sheath injection
subdural or subarachnoid injection
129
CNS eye block complications may occur following a needle block by 2 different mechanisms:
- unintentional intra-arterial injection
- unintentional subarachnoid injection
130
mechanism of complication oculocardiac reflex
trigeminal nerve (afferent, arc) to floor of 4th ventricle with efferent arc via vagus nerve
131
S/S oculocardiac reflex
bradycardia, other arrhythmias, asystole
132
intra-arterial injection
- may reverse the blood flow in the ophthalmic artery up to the anterior cerebral or ICA, so that an injected volume as small as 4cc may cause seizures
- symptomatic treatment by maintaining a patients airway; providing oxygenation; and abolishing seizure activity with small doses of benzos/prop/barb is usually adequate and results in a rapid recovery without sequelae
133
subarachnoid injection
- puncture of the dura mater sheath of the optic nerve or directly through the optic foramen results in partial or total brainstem anesthesia
- depending on the dose and volume of LA spreading toward the brainstem, subarachnoid injection can lead to bilateral block; cranial nerve palsy with sympathetic activation, confusion, restlessness; or total spine anesthesia with tetraparesis, arterial hypotension, bradycardia, and eventually respiratory arrest
- treatment is symptomatic (O2, vasopressors, and required intubation and ventilation) and should permit complete recovery after the spinal block wears off ( a few hrs)
134
ocular block evaluation
- after block is performed, partial movement of one or more of the ocular muscles may occur
- should evaluate to determine which muscles are involved and whether additional anesthesia is required
- analgesia of globe generally precedes akinesia of the eye
- can assess effectiveness of RBB 2 mins after administered; PBB 10 mins
135
what do use topical LA for?
anterior chamber (exp. cataract) and glaucoma operations rather than LA injections
136
facial nerve block
- regional blockade of oculi muscle (van lint method)
- prevents squinting
- obicularis oculi muscle must be blocked to complete immobilization of the eye
- 25 G, 4 cm needle inserted at position 1 until bone is contacted (inferolateral orbital rim)
- inject 1 mL LA
- reposition needle to positions 2 & 3 injecting 2-3 mL of LA respectively
137
typical regimen for LA application
- 0.5% proparacaine (aka proxymetacaine) LA drops, repeated at 5 min intervals for 5 applications, followed by topical application of an LA gel (lidocaine plus 2% methyl-cellulose) with a cotton swab to the inferior & superior conjunctival sacs
- ophthalmic 0.5% tetracaine
138
what surgeries is topical LA not appropriate?
posterior chamber surgery (exp. retinal detachment repair with a buckle) and it works best for faster surgeons using a gentle surgical technique that does not require akinesia of the eye
139
Strabismus
ocular misalignment or deviation of one eye relative to the visual axis of the other
140
cause of strabismus
refractive errors or muscle imbalance, rare causes include retinoblastoma, or other serious ocular defects and neurologic dx
141
what happens if strabismus is left untreated?
50% of children have some sort of visual loss because of amblyopia
142
how does surgery fix strabismus?
repositioning of the EOM's
strabismus correction is attempted early in childhood
143
when does visual maturation occur?
5 yrs old
144
pediatric patients undergoing strabismus surgery usally require
GA
145
most adult patients having strabismus surgery prefer
GA and have a satisfactory result with prop, remifentanil, 5HT3 antagonist, or dexamethasone and non-opiates for pain
some adults do well with a regional technique and IV sedation
146
PONV is common after surgery for
correction of strabismus
147
cataracts
are common causes of visual impairment in the older individual
pathogenesis is multifactorial but results in the opacity of the lens
148
extracapsular catract extraction aka
- aka phacoemulsification preferred method of modern cataract extraction
- performed through a small 3-4mm incision
- the nucleus of the lens are fragmented by an ultrasonic needle and then aspirated
- residual cortical material is removed
- removal of the lens with an intact posterior capsule provides for better positioning of an intraocular lens implant
149
intracapsular cataract extraction (ICCE)
is an older technique that completely removes the lens with the capsule through a much larger incision 12 mm
sometimes required for very dense cataracts and in areas of the world where modern ophthalmology equipment is not available
150
most cataract operations are performeed with
MAC and a topical or RA technique
151
glaucoma
- altered circulation of aqueous humor can produce an increase in IOP, termed ocular HTN
- ocular HTN with associated optic neuropathy and visual field loss
- commonly associated with an increase in outflow resistance
152
glaucoma forms
- acute (closed angle) glaucoma
- chronic (open angle) glaucoma
153
what meds are contraindicated in patients with glaucoma?
anticholinergic eye drops such as atropine cause mydriasis
however, IV atropine is minimally absorbed by the eye and is considered acceptable to use in these patients
154
Gonintomy
procedure performed to treat infantile glaucoma
- superficial incision is made in the trabecular meshwork to improve outflow of aqueous humor form the anterior chamger
- infants and children require GA for this
155
trabeculectomy
most commonly performed filtering procedure for adults
- block of limbal tissues is removed beneath a scleral flap, permitting outflow of aqueous
- antimetabolites such as mitomycin, can be injected intraop to help prevent surgical failures secondary to scarring
156
anesthesia for glaucoma surgery in adults usually performed witha __ __ or __ __ and, if needed a faciall nerve block
retrobulbar block; peribulbar block
157
many __ or __ have been used to divert auueous
tubes; shunts
- these implants are generally reserved for patients who have not responded to other management
- implants in current use have a plastic tube placed in the anterior chamber connected to a plate placed posterior to the limbus
158
diabetic retinopathy
- HTN and longer duration of diabetes are associated with an increased risk of DR
- the pathophysiology of DR is multifactorial; chronic high BG lead to vascular abnormalities, impaired auto regulation of blood flow with subsequent retinal hemorrhage and ischemia, as well as the accumulation of sorbitol and glyated proteins
159
what is one of the leading causes of visual loss worldwide?
diabetic retinopathy (DR)
160
earliest form of DR is
nonproliferative diabetic retinopathy (NPDR)
161
patients with DR may also manifest diabetic __ __
macular edema
162
on retinal examination of someone with DR they have
microaneurysms and hard exudates (leakage of protein and lipid)
microaneurysms may lead to hemorrhage whether in the. nerve layer or deep in the retina
163
some patients with NPDR will advance to
proliferative retinopathy
this stage is manifested by neovascularization arising from retinal vessels, the consequence of these fragile new vessels can be further hemorrhage fibrosis, and traction retinal detachment
164
2 main types of retinal detachment
- rhegmatogenous (tear)
- non-rhegmatogenous (no tear): tractional, exudative
165
symptoms of retinal detachment
- floater
- flashing light
- vision loss
- shadows, clouds
- curtain-like blackness
166
predisposing factors to retinal detachment
- advanced age
- diabetic retinopathy (HTN/DM)
- prior eye surgery
- vitreal dx
- myopia
167
treatment of retinal detachment
- vitrectomy
- scleral buckel
- gas fluid exchange
- injection of vitreous substitute
168
in retinal reattachment surgery, __ __ is injected into the operative eye to tamponade the retina onto the choroid layer form which it has become detached
sulfur hexafluoride
169
biochemical properties allows the gas bubble to remain in the operative eye for
7 to 10 days
170
__ from air diffuses into the bubble during this period of time, allowing it to expand but not to the point that it would raise IOP
nitrogen
however if patient is exposed to nitrous oxide, nitrogen can rapidly diffuse in the sulfur hexafluoride bubble and increase IOP
171
if NO is used in a retinal reattachment procedure
it must be turned off at least 15 to 30 mins propr to the injection of sulfur hexafluoride to prevent rapid expansion and potential increase of IOP
additionally, if patient is undergoing surgery in the immediate 2 weeks following this injection, nitrous is contraindicated
172
urgent/emergent surgery considerations
- risk of extrusion of ocular contents if increased IOP
- pulmonary aspiration (often traumatic injury)
- foreign body is common trauma (35% of all eye injuries)
- common in pediatric patients
173
walls of the orbit include:
frontal, zygomatic, greater wing of the sphenoid, ,axilla, palatine, lacrimal, ethmoid
174
where is the optic foramen located?
orbital apex
175
what does the optic foramen transmit?
optic nerve, ophthalmic artery, as well as the sympathetic nerves from the carotid plexus
176
superior orbital fissure transmits
- superior & inferior branches of the oculomotor nerve
- the lacrimal, frontal, and nasociliary branches of the trigeminal nerve
- the trochlear nerve
- the abducens nerve
- superior and inferior ophthalmic veins
177
inferior orbital fissure aka
contains what?
sphenomaxillary fissure
- infraorbital and zygomatic nerves & communication between the inferior ophthalmic vein and pterygoid plexus
178
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180
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