Ophthalmology Modified Flashcards
Where are ophthalmic procedures common?
ambulatory surgery centers (98.5%)
What are the common procedures of the eye?
lens and cataract (70%)
intraocular (10%)
eyelids, cornea, conjunctiva (10%)
Sclera
outer, fibrinous protective layer, white and opaque and lies just posterior to the cornea
Cornea
the outer, fibrinous protective layer located anteriorly, and it is transparent and colorless
Choroid
middle, vascular layer
Retina
the inner layer of the posterior half of the eye
Conjunctiva
a thin, transparent mucous membrane that covers the posterior surface of the eyelids and the anterior surface of the sclera
Anterior chamber
b/w cornea and iris
posterior chamber
b/w iris and lens
orbits
two symmetrical bony enclosures in the front of the skull
what is the visual axis
an imaginary line from the midpoint of cornea to midpoint of retina or macula
What is suspended in the anterosuperior part of the orbit
the globe
What are the three layers of the eyeball
large posterior segment (vitreous humor, retina, macula and root of optic nerve)
Small convex anterior segment (two chambers)
Anterior chamber: immediately behind cornea filled with aqueous humor that is produced by ciliary body
posterior chamber: contains the lens
How many muscles is the eye surrounded by?
6 extraocular muscles
Superior rectus muscle
moves the eye upward
supraduction
CN 3
inferior rectus muscle
moves the eye downward
infraduction
CN3
Medial retcus muscle
move the eyeball nasally (adducts)
adduction
CN3
Lateral recuts muscle
moves the eyeball laterally (abducts)
abduction CN6
Superior oblique muscle
rotates the eyeball horizontally towards nose and down
intorsion, depression CN 4
Inferior oblique muscle
rotates the eyeball horizontally towards temple and up
extorsion, elevation CN 3
What CNs supply the motor innervation to the eye?
CN 3, 4, 6
What does the optic nerve extend through?
optic canal
What does the optic nerve meet intracranially?
optic chiasm
What is the optic nerve covered by?
meninges, the fibrous wrappings of the arachnoid, dura, pia mater, which envelop the central nervous system, and surround by CSF
How does a total spinal occur from regional to the eye?
any anesthetic agent injected into the optic nerve sheath can find its way back to the midbrain through the CSF
Cranial Nerve 2
optic nerve
outgrowth of the brain
part of CNS
Cranial nerve 3
oculomotor nerve
primary motor nerve to the extraocular muscles
Cranial nerve 4
trochelar nerve
only orbital cranial nerve that enters the orbit from outside the muscle cone
Cranial nerve 5
trigeminal nerve
afferent pathway for oculocardiac reflex-> bradycardia and dysrrhythmias
what are the branches of CN5?
ophthalmic, maxillary and mandibular branches
sensory and motor
Ophthalmic branch provides
sensation of pain, touch, and temperature to the cornea, ciliary body, iris, lacrimal gland, conjunctiva, nasal mucosa, eyelid, eyebrow, forehead and nose
MAxillary branch
sensation of pain, touch and temperature to upper lip, nasal mucosa, scalp muscles
CN 6
abducens
motor function to lateral rectus muscle
CN7
facial nerve
upper branch further divides into the temporal and zygomatic branches, which innervate the orbicular muscles of the eye, the superficial facial muscles and scalp muscles
CN 10
vagus nerve
afferent pathway for the oculocardiac reflex-> bradycardia and dysrrhythmias
What muscles raise the upper eyelids?
levator muscles
orbicular muscle contracts the eyelid
What is normal intraocular pressure?
10-22mmHg
What is the most important determinant of IOP?
balance between production and elimination of aqueous humor, maintaining an average volume of 250ml
What decreases IOP?
IV and inhalation anesthetics
hyperventilation
hypothermia
hypotension
What increases IOP?
blinking, squinting succinylcholine (transient 5-10mmHg) ketamine (nystagmus) nitrous oxide atropine/scopolamine (acute angle closure glaucoma in susceptible patients) valsalva, pressure on eyeball, coughing, vomiting laryngoscopy/tracheal intubation hypercapnia, hypoxemia, hypertension
What is aqueous humor?
thin watery fluid that fills the space in the anterior chamber between cornea and iris
continually produced by ciliary body
drains out eye via trabecular meshwork into the aqueous veins and eventually into the veins of the orbit
What is the prupose of the aqueous humor?
nourishes the cornea and lens
gives the front of the eye its form and shape
What are common adult ophthalmic procedures?
cataract extraction occuloplastics (ptosis repair) cornea transplants or grafting trabeculectomy (for glaucoma) vitrectomy and retinal buckling trauma (enucleation or orbital fracture repair) LASIX
What is the leading cause of blindness in adults 20-74?
diabetes
What is the leading cause of blindness in children?
vitamin A deficiency
What are common pediatric eye cases?
strabismus exam under anesthesia retinoblastoma glaucoma cataracts retinal detachments
Strabismus
muscular surgery to fix ocular misalignment
Of the six muscles that innervate the eye, misalignment is present
can effect vision
Strabismus Anesthesia implications
it hurts! N/V multiple rounds for pediatrics emergence delirium oculocardiac reflex
What are common medications seen in strabismus surgery?
acetaminophen (15mg/kg)
ketorlac (0.5mg/kg)
fentanyl (as needed)
What is the oculocardiac reflex?
traction on the extraocular muscles of the eye, manipulation of the globe and pressure on the eyeball (increased IOP) cause bradycardia, sinus arrest, v fib, AV block, ventricular ectopy and negative inotropy
What is the physiology behind the oculocardiac reflex?
5th cranial nerve (afferent) to brainstem
10CN vagus efferent to cardioinhibitory center
What is the corneal reflex?
CN V (corneal touch) and CN VII (blink, orbicularis oculi)
What is the dose of atropine to help correct oculocardiac reflex bradycardia?
10mg/kg
Dark Adaptation and ERGs (electroretinograms)
Prior to EUA to assess the actual cones and rods and their functionality
Retinoblastoma
ocular cancer of retina primarily affecting kids under age 4
most curable, but increased risk of other cancers later in life
LMA will work for what procedures
radiation and procedures for retinoblastoma and strabismus
glaucoma
cataracts
Nasolacrimal duct probing
Amblyopia
Lazy eye
eye doesn’t work correctly in kids, message between teh eye and brain make it such that the worse eye kind of shuts off while the good eye does all the seeing
What happens if a lazy eye isn’t corrected?
when the brain focuses on the message coming from the good eye this can become permenant even if the weak eye is fixed
Who does amblyopia affect?
kids from birth to 7 years of age
How do you initially treat amblyopia?
eye patches or dilation drops on the stronger eye to force the weaker eye to work
Chalazion procedures
sty won’t go away and needs removal
zit on top of eyelid that wont go away
Nasolacrimal duct probing is
used to clear clogged tear ducts
Will you see stage 2 in eye surgery patients?
no
What should you travel to PACU with?
emergency drugs and a peds mask (propofol)
What are emergency eye cases?
open globes
corneal transplants melts causing open globes
canaliculi repairs
endopthalmitis
What is an open globe?
full thickness defect in the cornea (transplant outer covering) or sclera (white outer covering)
When should open globes go to surgery?
within 12-24 hours of surgery
Anesthetic considerations for globes
Dehydrated
GETA (succ can raise IOP, neccessity depends on NPO status, viable eye vs difficult airway)
Oral RAE tube
Antibiotics needed
What is a corneal transplant melts?
corneal transplant has rejected or the suture to the eye has come undone, leaving an opening to the eye
Anesthesia for a corneal transplant melt?
GETA
LMA vs ETT will depend on severity of melt
Anesthesia considerations for canaliculi repairs
younger children from dog bites/stratches
can be inner or outre
assuming NPO and patient appropraite can be LMA
fairly quick procedures
Endopthalmitis
infection of the tissues or fluids inside the eyeball
infection in the vitreous
Surgical considerations for endopthalmitis
vitrectomy to remove some of the infected vitreous gel and inject antibiotics
discuss anesthesia with surgeon, possible with peribulbar block but may not if infection too bad
Ophthalmology and General anesthesia
retina cases
consider oral rae tube
MAC/PBB/RBB cases?
anesthesia provides sedation, surgeon places block in OR to prep
MAC/Cutdown
used on patients on anticoagulants and unsafe to use PBB/RBB
Done like a cataract from our standpoint. Use sedation and tetracaine gtts and once the surgeon drapes they will inject local by cutting the conjunctiva and placing local in back of eye. A little different than a peri-bulbar block but achieves same idea of localization.
We do these if patient’s are on anticoagulants to reduce risk of bleeding. Also some surgeons just prefer them because of less risk associated with them
Topical Anesthesia
tetracaine drops only with sedation PRN
Take away for eye cases
Use oral RAE tube for ETT N/V common paralysis rarely required Smooth induction smooth emergence
Anesthesia tips for emergency eye cases
if patient awake, ensure comfortable
no airway
Local in helpful
What should be placed if doing an extensive open globe case?
foley up front
Ocular regional anesthesia is effective for
analgesia and akinesia of the eye and eyelids
What nerves does Ocular regional anesthesia effect?
CN 3,4, 5,6, 7
What is the anesthetic used for Ocular regional anesthesia?
versed and fentanyl +/- small propofol doses to get patient through actual block
Retrobulbar block
Needle inserted through the skin in the infratemporal area, just above the inferior orbital rim and advanced toward the orbital apex deep into the muscle cone (retrobulbar space)
2-4ml of LA
better akinesia
Complications of RRB
trauma to optic nerve, blood vessels, globe
retrobulbar hemorrhage b/c anesthetic is put inside the orbital epidural space
spread of LA to CSF causing hemodynamic instability and respiratory depression within 5 minutes
seizures if intravascular
Peribulbar Block
may require an injection above or below the orbit (although most of our surgeons just do one below)
8-12ml
anesthetic is injected, creating positive extraconal pressure that spreads the agent inside the muscle cone to anesthesize the cranial nerves (avoids muscle cone and vital structures)
What is a safer choice block and why?
PBB b/c of less risk of hemorrhage and central spinal
What is the max dose of tetracaine?
3mg/kg
How do you administered tetracaine?
2-6 drops (divided doses 1-2 minutes apart) in the eye prior to prep
Sub-tenon Block
greater analgesia than motor block
block performed between rectus muscles of the globe
conjunctiva incised-> tenon tissue is elevated and incised-> a short cannula is inserted into the sub-tenon space
3-4 ml to achieve analgesia
larger doses may give akinesia
What is tennon tissue?
tissue that encapsulates the globe posteriorly and fuses with the conjunctiva anteriorly
What is the objective of the sub-tenon block LA placement?
to get posterior spread of the agent
What are ophthalmic medications that cause dilation?
atropine/scopolamine
epinephrine
phenylephrine
cyclopentolate
What class is atropine/scopolamine?
anticholinergic
What are adverse effects of atropine/scopolamine?
central cholinergic syndrome
scopolamine can cause disorientation in some patients
What is epinephrine?
sympathetic agonist
What are side effects of epi?
tachycardia, arrhythmias, HTN, headache
What is phenylephrine
alpha agonist
What are side effects of phenylephrine?
HTN, arrhythmias, headache, reflex bradycardia
What is cyclopentolate?
synthetic anticholinergic
What are side effects for cyclopentolate?
disorientation, psychosis, seizures
What ocular medications cause miosis?
pilocarpine
carboachol
physostigmine
echothiopate
What is pilocarpine? Side effects?
muscarinic alkaloid
redness of sclera, irritation
What is carboachol? Side effects?
synthetic carbamyl ester of choline
used if not responsive to pilocarpine
What is physostigmine? side effects
indirect acting anticholinesterase
miosis
What is echothiopate? side effects?
indirect acting organophosphorus cholinesterase inhibitor
increases drainage of intraocular fluid and used to treat glaucoma
irreversibly binds to cholinesterase (effects will last for weeks)– will prolong succinycholine
What are ophthalmic glaucoma medications?
timolol acetazolamide echothiopate iatanoprost brimonidine
What is timolol? side effects?
potent non-selective beta blocker
bradycardia, asthma, CHF
What is acetazolamide? Side effects?
carbonic anhydrase inhibitor
mild diuretic, hypokalemia, acidosis, hematuria, paresthesia, gastric disease, flaccid paralysis, seizures
avoid with hepatic renal disease
What is iatanoprost?
prostaglandin
What is brimonidine?
alpha 2 agonist
How does acetazolamide (diamox) work?
used to lower the pressure in the eye by lowering the amount of aqeous humor production in front of the eye
What is the dose of acetazolamide?
250-500mg mixed with normal saline
What is special about acetazolamide?
incompatible with IV and other medications (precipates with zofran)
Who can not have acetazolamide?
pateints with a sulfa allergy
How do topical eye medications enter the bloodstream?
through the outer eye membrane and lacrimal apparatus
How can you reduce the amount of topical medications that enter the bloodstream?
patient closes eyes for 60 seconds
avoid blinking
block the tear outflow canal by placing the index finger over the medial canthus after the eye is closed
What are ophthalmic complications?
retrobulbar hemorrhage intravascular LA injection globe puncture optic nerve sheath trauma ocular ischemia extraocular muscle palsy and ptosis facial nerve block oculocardiac reflex corneal abrasion central retinal artery occulsion
Preoperative considerations for ophthalmology
can the patient lie supine for a long time?
evaluate claustrophobia, chronic pain, COPD, tremors, mental status (anxiety, inability to cooperate)
postnasal drip, vasoconstrictive nose drops
What is the cause of sudden onset of nausea at home after procedure?
increased intra-ocular pressure than anesthetic medications
What is intraocular gas?
retinal procedures may utilize sulfur hexafluoride
is not removed will dissipate in 10-14 days
What needs to be discontinued 15 minutes prior to gas injection?
nitrous oxide
Cautions of intraocular gas
can not fly or go to high altitudes
if needing general anesthesia within 14 days no N2O
may be required to lie face down during recovery
