Ophthalmic Surgery Flashcards by Andrew Skuta

3 wall layers of the Sphere of the eye

-sclera
-uveal tract (middle)
-retina

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Outermost layer, tough, fibrous, white of the eye

Sclera

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Most anterior part of the sclera

Cornea

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Most focus power of the eye?

Curvature of the cornea

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3 structures of the Middle Layer of the eye

Choroid
Ciliary Body
Iris

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Middle: layer of blood vessels, located posteriorly

Choroid

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middle: behind iris, produces aqueous humor

Ciliary body

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middle: pigmented, controls light entry

Iris

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iris dilator muscle contracts (dilitation or mydriasis)

sympathetic stimulation

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stimulation iris sphincter muscles contracts (pupillary constriction or miosis

parasympathetic stimulation

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Retina characteristics

-inner most layer

-Photoreceptors
Light activates to produce neural signal

No capillaries
Choroid layer provides oxygen
Detachment from choroid compromises blood supply & is major cause of vision loss

Retina ends 4 mm behind the iris
Pars plana
area between limbus (edge) of cornea and end of retina

Safe entry area for vitrectomy procedures

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____ has no capillaries and detachment from the ______ compromises blood supply and is major cause of ______ ______.

Retina
choroid
vision loss

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Retina: safe entry for vitrectomy procedures

Pars plana

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center: traction of vitreous on _____ causes detachment

retina

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Scarring, bleeding or opacification of vitreous is treated with ______

vitrectomy

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6 extraocular muscles:

superior rectus
inferior rectus
medial rectus
lateral rectus
superior oblique
inferior oblique

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located at 12 o’clock-moves eye upward or supraaducts the eye

-superior rectus

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: 6 o’clock – moves eye downward, or infraducts

inferior rectus

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90 degrees from 12 o’clock in given direction. Medial – adducts, Lateral – abducts

medial and lateral rectus

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rotates the eye and depresses the eyeball

superior oblique

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– rotates the eyball on its horizontal axis temporally, or extorts the eye and elevates the eyeball

inferior oblique

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(My ____ &______ ______muscles are in great shape-I only roll my eyes a 100 times a day)

superior & inferior oblique

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All ocular muscles originate in the ___ ______ around the ______ __ _____, except for the _____ _____.

-orbital apex
-annulus of Zinn
-inferior oblique

TEST question!

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Symptoms of OCR (ocular cardiac reflex)

Bradycardia
AV block
Ventricular ectopy and asystole

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OCR seen especially with _____ _____ traction

medial rectus Can occur with any stimulation of orbital contents including lid and periosteum

OCR reflex is ________. _______impulses originate in orbital contents (via long and short ciliary nerves) _______ limb is vagus nerve to the heart limb is vagus nerve to the heart

trigeminovagal Afferent Efferent

OCR is more frequent in ____ vs _____.

peds vs adults

Path of OCR: Afferent impulses originate in _____ ______ (via long and short ciliary nerves) -to _____ ______ -to ________ division of the _______ nerve -to sensory nucleus of _______ nerve near _______ ventricle -to _______ motor nuclei of the ______ -Efferent limb is ______ nerve to the ______.

-Afferent impulses originate in orbital contents (via long and short ciliary nerves) -to ciliary ganglion -to opthalmic division of the trigeminal nerve -to sensory nucleus of trigeminal nerve near fourth ventricle -to visceral motor nuclei of the vagus -Efferent limb is vagus nerve to the heart

OCR response made worse by:

hypoxemia an hypercarbia

Treatment of OCR

-ask surgeon to stop manipulation -assess ventilation -lidocaine local or deepen anesthetic -persistent bradycardia --> atropine -pretreat with glyco or atropine but consider patients with conduction block or BB

Blood supply to eye dependent on _____ ______ pressure MAP less IOP. _____ less than ____

intraocular perfusion pressure MAP less than IOP

_______ IOP therefore impairs blood supply and optic nerve function IOP therefore impairs blood supply and optic nerve function

High

The quantity of ____ and ____ volume regulates IOP

aqueous and blood volume

Normal IOP: > __mmHg is pathological

10-22 mmHg 25

aqueous humor production is constant and facilitated by ______ _______.

carbonic anhydrase

_______ IOP leads to fluid accumulation in the eye

Decreased

_______ IOP leads to ocular htn and structural changes (ie atrophy of optic disc and nerve fibers, optic artery occlusion)

Increased

Sudden _______ in BP increases IOP, but this soon dissipates due to drainage system

increases

Sudden decreases in BP < ____ will drop IOP d/t loss of auto regulation. __ Systolic causes 3-4 torr decrease in IOP from decreased blood flow in nl eye

90 60

Anesthetic events that Incr BP :

: laryngoscopy & Intubation, trendelenburg positon

IOP may increase up to ___x with coughing

40x

Venous pressure: Increase in ___ increase ____, even more than increase in BP.

CVP IOP

Direct pressure on the eye from compression in the prone position (coupled with lower systolic bp) has been indicated in _____ ____ ______

Post-op vision loss

A fast respiratory rate may ______ IOP from insufficient ______ _____

increase venous drainage

Decreased PaCo2 results in a fast drop in IOP from _____ _______ ________ PaCO2 results in a slow increase in IOP

choroidial vasoconstriction Increased

______ _______ decreases the choroid vessel volume and therefore IOP ______ _____ increases the choroid volume and the IO

Metabolic acidosis Metabolic alkalosis

External Forces : pressure to the globe may increase IOP Forced lid squeeze (up __ mmHg) Blinking (up __mmHg)

50 mmHg 5 mmHg

Most anesthetic drugs ___ or have no effect on IOP

lower

Inhalation agents drop IOP by

lowering BP and thereby decreasing choroidal volume relax extraocular muscles and lower wall tension Pupil constriction enables aqueous outflow

IV agents______ and ______decrease IOP

propofol, thiopental

______ may increase as it usually raises BP and doesn’t relax extraocular muscles (NYSTAGMUS)

Ketamine

________ is associated with myoclonus (10-60%) and may not be appropriate with an open globe

Etomidate

_________does increase IOP

Succinylcholine (Sch) Starts w/n 1 minute Increases 5-10 mmHg for 5-10 minutes d/t prolonged contracture of extraocular muscle Glaucoma pt reportedly has similar response to Sch, not exaggerated or prolonged

.........decreases aqueous production by inhibiting Na pump responsible for secretion of aqueous humor, decreasing IOP

Carbonic anhydrase inhibitor: Acetazolamide (diamox)

...........used IV introp to drop IOP. Increases circulating blood volume (CHF) and pt may require urinary catheter. Max effect 30-45 minutes, returns to baseline 5-6 hours

Osmotic diuretic: Mannitol

_______topical anticholinesterase drug maintain miosis to Rx glaucoma. Systemic absorption leads to total inhibition of plasma cholinesterase. Prolonged muscle paralysis after ______

Echothiophate Succinylcholine!

______ dilates pupil

Neo

Topical Beta blocker, use for glaucoma. Systemic absorption can cause bradycardia, bronchospasm, and CHF exacerbation

Timolol

______ and _____ are cholinergic drugs used to constrict pupil.

Pilocarpine and Acetylcholine

Na less than ____mEq/L greater than _____. K less than ____ mEq/Lor greater than ___. CANCEL CASE

120 158 2.8 6.2

glucose: Critical result: less than ___ mg/dl or greater than ___ mg/dl > __ CAN STILL CANCEL

46 484 > 250

Facial nerve block blocks the _____ _____ muscle Utilized when complete akinesis of eyelids desired (can’t squeeze eye, can’t squint)

orbicular oculi

_____ _____Blocks entire trunk of facial nerve Expect....

Nadbath Rehman Expect lower facial droop postop for several hours. Injection is close to vagus and glossopharyngeal nerve. Associated w/ vocal cord paralysis, laryngospasm, dysphasia and resp. distress

RBB most common complication

retrobulbar hemorrhage

Proptosis is....

downward displacement)and subconjunctival ecchymosis

RBB: _____ _____ can still occur with negative aspiration

intravascular injection

RBB: injection into optic nerve sheath leads to:

contralateral amaurosis (complete lack of vision) obtundation respiratory arrest (occurs w/n 20 minutes resolves w/n an hour) vascular collapse from depressant effect on the medulla (total spinal)

Safer approach to RB block? Increased likelihood of_____

Peribulbar Block less risk of hemorrhage ecchymosis

Choice of general vs regional made on basis of: duration, relative risks & benefits, and pt preference. Neither shown to be safer (except in the case of ____ ____ general ett only choice)

rupture globe

GA coals:

Goals: smooth induction, stable IOP, avoid severe OCR, motionless field, smooth emergence

GA: Emesis from vagal stimulation, esp. after _______ surgery common

strabismus surgery,

GA: Severe pain post op is unusual after eye surgery except for ______, ______, ______.

scleral buckling, enucleation, and ruptured globe repair.

N20 considerations:

In certain vitreoretinal procedures, an air bubble is injected into the eye to tamponade the detached retina into the globe. N2O diffuses and causes air bubble expansion, with potential for IOP increase. N2O should be d/c’d 15 minutes before placement of sulfur hexaflouride and avoided for 7 to 10 days after. Another vitreal air agent, perfluoropropane (C3F6) persists for weeks. Avoid N2O for one month after instillation of this agent! If a hx of recent retinal surgery establish if invitreal bubble used before using N2O.

Open globe anesthesia induction

usually full stomachs controversy for succs generally taught to NOT use Succinylcholine