Ophthalmic Flashcards

Question

Superior Oblique

Answer 1

Cranial nerve IV | Intorsion, depression

Answer 2

Cranial nerve III | Extorsion, elevation

Answer 3

Aqueous humor dynamics - balance b/w production & elimination Changes in choroidal blood volume - vascular meshwork in the posterior chamber ↑venous blood pressure Extraocular muscle tone

Answer 4

Thin, watery fluid that fills the space in the anterior chamber b/w the cornea & iris - Nourishes the cornea & lens - Gives the anterior eye form & shape Continually produced by the ciliary body (lies behind the iris) Drains out via trabecular meshwork into the aqueous veins & then into orbit veins

Answer 5

``` Eyelid muscle contraction Blinking 5mmHg Squinting 26mmHg Cardiovascular or respiratory variables (CVP, ABP, PaCO2) *Laryngoscopy & intubation External pressure Positioning - prone Succinylcholine Topical anticholinergics ```

Answer 6

``` Volatile anesthetics IV anesthetics (exception: Ketamine) Non-depolarizing muscle relaxants Benzodiazepines Narcotics ```

Answer 7

↑IOP 5-10mmHg for 5-10 minutes MOA unclear Result from prolong extraocular muscle contraction? No consistent method to prevent increase Pediatric laryngospasm dose 4mg/kg IM or 1-2mg/kg IV (10mg)

Answer 8

Afferent transmission via Trigeminal nerve V Efferent transmission via Vagus nerve X Pull on muscle → bradycardia Causes - pain, pressure, or eyeball manipulation Traction on medial rectus muscle common

Answer 9

``` Cardiac dysrhythmias (bradycardia, sinus arrest, V-fib, AV block, ventricular ectopy) Negative inotropy ```

Answer 10

Pediatric strabismus surgery

Answer 11

Anticholinergics pre-treatment (?) Stop the stimulus or release pressure Administer Atropine 10mcg/kg or Glycopyrrolate LA infiltration into medial rectus muscle

Answer 12

Small gas bubble injected into posterior chamber to hold retina in place Sulfur hexafluoride most commonly used - Inert, poorly diffusible gas - Less soluble in blood than nitrogen & N2O - DOA 10 days Bubble expands 2x in 24 hours Discontinue N2O 20 minutes prior to injection to allow washout Avoid N2O 10-14 days after sulfur hexafluoride

Answer 13

``` IRREVERSIBLE cholinesterase inhibitor Glaucoma treatment Systemic absorption → ↓plasma cholinesterase activity Lasts 3-6 weeks after discontinuation Succinylcholine prolonged 20-30 minutes Extend ester local anesthetics duration ```

Answer 14

Enter bloodstream via outer eye membrane & lacrimal apparatus Close eyes 60 seconds after gtt instilled to improve absorption Avoid blinking Block tear outflow canal (place finger over medial canthus)

Answer 15

Cataract & vitreoretinal surgeries

Answer 16

Peribulbar block Retrobulbar block Facial nerve block

Answer 17

Inject LA outside the muscle cone Injection above and/or below orbit Provides eye analgesia & akinesia Typically more patchy - requiring additional supplementation throughout the case (request surgeon admin more LA) Relatively low complication rate Safer choice d/t less hemorrhage & central spinal risk

Answer 18

``` ↑volumes injected 6-8mL ↑IOP Slower onset (5-10 minutes) Possible globe perforation Vertical diplopia (myotoxicity from LA) ```

Answer 19

Patient looks straight ahead Avoid vasculature & optic nerve Dull, short-beveled 25-27G 22mm needle Insert needle lateral aspect of the inferotemporal quadrant & superior-nasal ASPIRATE slowly before injection Inject 6mL local anesthetic Lidocaine + Bupivacaine (+/- Epi 1:400,000)

Answer 20

Inject LA inside the muscle cone Provides eye analgesia & akinesia* (better akinesia for surgeon) ↑complication rate as compared to peribulbar block Hemorrhage risk d/t anesthetic injection inside the muscle cone

Answer 21

Insert 25G needle through lower lid at lateral third junction & medial 2/3 inferior orbital edge Advance 25-35mm (19-31mm safest) toward orbit apex ASPIRATE & inject 2-5mL local anesthetic Lidocaine & Bupivacaine most common

Answer 22

``` 1:500 blocks Trauma to optic nerve Vision loss *Retrobulbar hemorrhage Globe perforation Oculocardiac reflex Brainstem anesthesia (injection into optic nerve sheath) - Central LA spread to CSF causing hemodynamic instability & respiratory depression w/in 5min IV or intra-arterial injection Seizure Respiratory or cardiac arrest *Usually occur w/in 15 minutes after block ```

Answer 23

Bleeding disorders Anticoagulation Extreme myopia Open eye injury

Answer 24

Local anesthetic placed into potential space b/w tenon's capsule & sclera Inferonasal conjunctival fornix most commonly used Direct needle posteriorly following globe curve Superficial injection allows LA to spread circularly around scleral globe portion (3-5mL) Larger volume (8-11mL) allows spread to extraocular muscle sheaths Deep injection - posterior intra & extraconal spaces (2-5mL) most common

Answer 25

Facial nerve periocular branches | Prevent excessive blinking during eye surgery

Answer 26

``` Pediatric patient Uncooperative patient Severe claustrophobia Inability to communicate Inability to lie flat Open-eye injuries Procedures w/ duration > 2 hours ```

Answer 27

``` Nausea/vomiting ↑IOP Aspiration Complications 2° to medical problems (i.e. cardiovascular disease) Time $$$ ```

Answer 28

Synergistic effects Pediatric/elderly dosing Circulation time

Answer 29

``` Block sedation (short-acting agents) Sedation not required w/ adequate block Rotate HOB 90-180° Standard monitors Oculocardiac reflex Temperature Fluids Consider "light" GA w/ stimulation Hypotension Oxygen & cautery → airway fire risk Corneal abrasion risk Retinal artery occlusion ```

Answer 30

PONV (especially pediatrics) Postop eye pain unusual - indicates corneal abrasion or acute intraocular HTN (treat w/ Mannitol or Acetazolamide) Elderly patients w/ MI history ↑risk ischemic events even under LA - consider periop β blockers

Answer 31

Ocular misalignment Intervention before 4mos to allow normal stereoscopic visual development ↑MH risk associated w/ underlying myopathy Avoid triggers

Answer 32

Strabismus

Answer 33

Lengthens/shortens ocular muscles to straighten eyes & allow binocular vision 30-60 minutes General anesthesia Minimal EBL PONV prevention - hydration, ↓opioids, avoid N2O, Propofol, LA infiltration near extraocular muscle, antiemetics (Decadron 0.1mg/kg or Zofran 0.1mg/kg) Painful procedure - Tylenol 15mg/kg, Toradol 0.5mg/kg, & Fentanyl 1-3mcg/kg

Answer 34

Full stomach precautions Aspiration risk Prevent ↑IOP

Answer 35

``` Full-thickness cornea (transparent outer covering) or sclera (white outer covering) defect Emergency surgery w/ GA Succinylcholine risk vs. benefit Laryngoscopy & intubation ↑IOP Antibiotics - Vancomycin & Zosyn ```

Answer 36

Do NOT attempt to evacuate contents w/ NG tube preop Admin Metoclopramide IV, H2 antagonists (Ranitidine), and/or non-particulate antacid prior to induction Do NOT attempt regional anesthesia LA injection ↑IOP Attempt RSI w/ cricoid pressure & avoiding PPV Extubate awake, spontaneously breathing, & head turned to side

Answer 37

``` AVOID direct pressure on eye AVOID Trendelenburg position AVOID regional anesthesia AVOID ↑CVP AVOID drugs ↑IOP AVOID agitation in young children ```

Answer 38

``` Retrobulbar hemorrhage Globe puncture Optic nerve sheath trauma IV injection Ocular ischemia Extraocular muscle palsy & ptosis Facial nerve blocks Oculocardiac reflex Corneal abrasion Central retinal artery occlusion d/t prolonged pressure ```

Answer 39

Results from trauma to an orbital vessels Moves eyeball forward Venous hemorrhage - slow onset Arterial - rapid onset & pronounced proptosis Treatment: - Digital pressure - Lateral canthotomy (cut lateral canthus) ↑orbital space → place hemostat in temporal direction along lateral canthus 4-6mm & clamp hemostat, use scissors to incise the crush marks left by hemostat, control local bleeding

Answer 40

↑IOP caused by injection (sharp or dull needles) Risks include myopic eye, scleral thinning, scleral buckling, & sclera bulging Prevention - avoid supranasal gaze position, direct needle away from globe axis during insertion, insert needle slowly w/ bevel towards globe, never forcefully inject LA, use modified techniques S/S ↑resistance to injection, pupil dilation/ paralysis, ↑IOP, hemorrhage

Answer 41

Optic nerve sheath surrounds the optic nerve - Outer sheath contains dura mater - Inner sheath consists arachnoid & pia mater Subarachnoid space contains CSF & continuous w/ optic chiasm Dura splits into 2 layers at optic foramen Inner layer forms optic nerve dural covering & forms orbital epidural space *Observe contralateral pupil block Contralateral pupil constricted → dilated after block → assume subarachnoid/subdural injection & prepare for respiratory arrest

Answer 42

Retinal vascular occlusion or thrombosis reported after ocular blocks ↓pulsatile ocular blood flow after blocks Optic nerve atrophy reported after regional block or GA Transient optic nerve injury symptoms - include contralateral amaurosis or respiratory arrest or vascular occlusion/thrombosis → vision loss

Answer 43

Inferior muscle palsy reported after retrobulbar anesthesia Persistent vertical diplopia (double vision) Surgical intervention indicated Prevention - avoid needle contact w/ extraocular muscles, avoid deep orbital penetration, avoid angling needle toward visual globe axis LA myotoxicity may cause postop diplopia and/or ptosis

Answer 44

Cranial nerve VII Bell's palsy 2° to direct nerve trauma S/S - dysphagia, hoarseness, coughing & respiratory distress Vagus, glossopharyngeal, & spinal accessory nerves close proximity Prevention: - Avoid large volume LA - Avoid Nadbath block technique in certain patients - Airway concerns → intubate

Answer 45

When the eyeballs move upward & outward in response to the eyes being forcefully closed Protective reflex to prevent corneal injury AKA "belling" Requires MAC 1.8 to abolish this reflex

Answer 46

``` EUA Dye used to visualize the retina images & leaks around corneal surgical sites Dose 5-7mg/kg IV push fast (similar to Adenosine) Wear gloves when prepare & admin ```

Answer 47

``` Ocular retina cancer 1° affects children < 4yo Tumor present in the eye or bilateral Curable, but ↑risk cancers later in life Monthly check-ups EUA → laser or cryotherapy ```

Answer 48

Lazy eye Children 0-7yo Initial treatment w/ eye patches or dilation drops on the stronger eye to force the weaker eye to work

Answer 49

Corneal transplant rejected or suture to the eye has come undone, leaving an opening to the eye General anesthesia LMA or ETT dependent on melt severity Surgical treatment - few sutures or completely remove the original transplant & replace w/ new one

Answer 50

Inner or outer canthus repair Common in younger children from dog bites or scratches Fairly quick procedure Performed by plastic surgery resident

Answer 51

Tissue or fluid infection INSIDE the eyeball Surgery performed after patient not responded to conservative measures → infection now in the vitreous Vitrectomy performed by retina surgeon to remove infected vitreous gel & inject antibiotics into the eye Possible peribulbar block however not effective in severe infections

Answer 52

``` Local anesthetic gtt Numbing eye drops - Eye only holds 0.5mL - Admin 2-6 drops divided in doses 1-2min apart Utilize w/ PRN sedation ```

Answer 53

Acetazolamide Carbonic anhydrase inhibitor used to lower IOP ↓aqueous humor production in anterior eye Adult dose 150-500mg Mix w/ NS Admin at end procedure IV incompatible w/ Zofran Contraindicated in patients w/ Sulfa allergies