Eyes Flashcards
Where is the anterior chamber?
between the cornea and iris
filled with aqueous humor produced by ciliary body
where is the posterior chamber?
between the iris and lens
contains lens
What is strabismus?
ocular misalignment
how many muscles are on each eye? and what are they?
6
superior, inferior, medial, lateral rectus
superior and inferior oblique
Concerns with strabismus surgery?
Pain
N&V
Emergence Delirium (opthalamic + short)
Occulocardiac reflex
How do we treat pain from strabismus surgery?
tylenol 15 mg/kg
tetracaine prior to prep
toradol 0.5 mg/kg
fentanyl PRN
Decadron and Zogran dosing for pediatrics
0.1 mg/kg
What is the cause of oculocardiac reflex
Muscle pulled = bradycardia
Lots of pressure on eye = bradycardia
AFFERENT - Trigeminal (5)
EFFERENT - Vagus (10)
What is the first thing you do for OCR
Tell them to stop
Atropine (10 mcg/kg) or Glycopyrrolate
Local anesthetic (very rare)
When should you pretreat with anticholinergics?
Down’s Syndrome
Adult w/resting HR 40
What is the laryngospasm dosing
Succs 4 mg/kg IM and Atropine 0.2 mg/kg
Succ 2 mg/kg IV (reality, give 10 mg)
Exam under Anesthesia?
Done on their own, or in conjugation w/another surgery
Duration: 1 minute - 2 hours
Used to evaluate kids that can’t tolerate eye exams in the clinic, muscle tightness prior to strabismus, cancer treatment, etc.
What is Bells Phenomenon?
When the eyeballs move upward and outward when forcefully closed. It is what the body uses to protect the cornea.
Most often seen during speculum insertion & traction on the muscles
What amount of MAC is needed to abolish Bell’s?
1.8
EUA exam tips
Lots of gas, then no gas, then lots. LMA. Fluorescein.
usually just need tylenol
What is Fluoresceein?
bright yellow dye used to see retina images and leaks around corneal surgical sites
5 - 7 mg/kg (push like adenosine)
What is an ERG?
Electroretinograms
These are done prior to an EUA to assess the actual cones and rods and how functional they are.
Put them to sleep, cover eyes for 20 minutes, just wait.
TIVA bby
What is retinoblastoma?
Occular cancer of retina affecting kids < 4 (usually). There is a tumor in the eye (1:3 are bilateral). Genetic? Sometimes. Usually, no family hx. Frequently from Huntersville, NC.
Curable… but increased risk of other cancers later in life..
Retinoblastoma sx in peds
Start as an EUA - may or may not need laser or cryotherapy once the tumor is seen
Retinoblastoma sx in adults
MAC + block
Radiation pellets
Amblyopia
lazy eye
affects kids 0 - 7
eye patch, dilation drops
cataracts
in kids - GA + tube b/c they are intense
may or may not need a lens replacement
Chalazion
sty removal
quick + LMA
Premed dosing
versed 0.5 mg/kg PO 15 - 30 m before surgery
Emergence Delirium RF
eyee
< 1 hour
rapid wakeup
sevo
When does precedex peak?
20 m
remember, it loweers BP
Retina case
TUBE + PARLYZE
Open Globe
emergent ( surgery w/i 12 - 24 h)
severity can range from a small laceration (few stitches) to full retina exploration
definition: full thickness defect in the cornea or sclera
Anesthesia Considerations for an Open Globe
- Dehydrated patient
- GA + ETT
- Oral Rae (unless > 6 ft, b/c an 8.0 won’t be long enough)
- Probs the only eye case that needs antibiotics
ABX for Open Globe
Vanc
Zosyn
Corneal Transplant Melts
Corneal transplant has rejected or suture has become undone… leaving an opening to the eye
Corneal Transplant Melts Anesthesia
GA - if patient coughs, the eye contents will extrude
LMA vs ETT (depends on severity of eye)
Don’t block these patients
Canaliculi Repair
Usually from dog bites
NPO status is good, so use LMA
quick procedure
Endopthalmitis
Infection of the tissues or fluids INSIDE the eyeball
Retina surgeon does a vitrectomy to remove infected vitreous gel and inject abx into the eye
Block or no block depending on extent of infection
Endopthalmitis Anesthesia
GA - ETT (retina cases)
Lasts 3 - 4 hours
Potentially MAC (PBB/RBB)
When do you use paralytics
Only if coughing would cause a major problem (i.e. retina or open globe)
RBBB
- less volume
- more chance of hemorrhage b/c anesthetic is placed inside muscle cone
- spread of LA into CSF = death in 5 m
- better akinesia for the surgeon
PBB
- may require an injection above & below the orbit
- can be patchy (may need to ask fo more local)
- safer
Mac/Cutdown
aka topical anesthetic
2 - 6 tetracaine drops (in divided doses 1 - 2 minutes apart) prior to prep
eye can only hold 1 mL at a time
extensive opeen globe case
consider a foley!!!
Diamox (Acetazolamide)
carbonic anhydrase inhibitor used to lower pressure in the eye by lowering the amount of aqueous humor production in front of eye
Dose: 250 - 500 mg Mix w/NS Give at end of the case DONT GIVE WITH ANOTHER DRUG ESP. ZOFRAN CONTRAINDICATED W/ SULFA
just drops with kids
what is the leading cause of new cases of blindness among adults
DM (age 20 - 74)
Cataracts (worldwide)
What is the annulus of Zinn?
tissue ring around the optic nerve
good landmark for point of insertion of many muscles
What is the volume of each adult orbit?
30 mL
an orbit contains an eyeball (globe) + other structures
Opthalmic artery
first branch of internal carotid, passes into orbit through optic canal (lies inferolateral to optic nerve)
What is the visual axis?
Optic axis
Imaginary line from the midpoint of cornea to midpoint of retina/macula
What is axial length?
A measurement of the visual axis.
Measured preoperatively to determine appropriate intraocular lens.
Normal axial length
23 - 23.5 mm
Hyperopia
Farsighted
< 22 mm
Myopia
Nearsighted
> 24 mm
increased chance of puncturing globe
What is in the posterior segment?
vitreous humor, retina, macula, root of optic nerve
Name CN involved in vision
2-7, 10
2 = optic 3 = occulomotor 4 = trochlear 5 = trigeminal 6 = abducens 7 = facial 10 = vagus
OPTIC N
CN 2
Orbital portion of the optic nerve is 25 - 30 mm long
Travels posteriorly within the muscle cone
4 mm diameter; outgrowth of brain
Covered by meninges
Central retinal artery & vein surround the nerve
Occulomotor N muscles
Inneervates superior rectus, inferior rectus, medial rectus, inferior oblique, and levator
CN III PSNS vs SNS
PSNS to ciliary ganglion & pupil constriction
SNS to pupil dilation
Trochlear nerve
motor fibers to superior oblique muscle
what is unique about cn 4
enters orbit from outside muscle cone
CN 5
sensory + motor
forms trigeminal ganglion
three divisions of trigeminal nerve
opthalmic (lacrimal, frontal, nasociliary)
maxillary
mandibular
abducens n
CN 6 to lateral rectus
facial nerve
motor to facial muscles
vagus
efferent pathway for OCR
superior rectus
supraduction (3)
inferior rectus
infraduction (3)
medial rectus
adduction (3)
lateral rectus
abduction (6)
superior oblique
intorsion, depression (4)
inferior oblique
extorsion, elevation (3)
what raises the upper eyelids
LEVATOR
what contracts the eyelid
orbicular
what raises ICP
squinting, contraction of levator or orbicular