Ch 44 Objectives Flashcards
(312 cards)
1
Q
What is the function of the Superior rectus muscle?
A
Elevates the eye; upward (supraduction)
Position: 12 o’clock, Cranial Nerve: III
2
Q
What is the function of the Inferior rectus muscle?
A
Depresses the eye; downward (infraduction)
Position: 6 o’clock, Cranial Nerve: III
3
Q
What is the function of the Medial rectus muscle?
A
Moves eye nasally (adduction)
Position: 3 o’clock (medial), Cranial Nerve: III
4
Q
What is the function of the Lateral rectus muscle?
A
Moves eye laterally (abduction)
Position: 9 o’clock (lateral), Cranial Nerve: VI
5
Q
What is the function of the Superior oblique muscle?
A
Rotates the eyeball on its horizontal axis toward the nose (Intorts and depresses the eye)
Position: Via trochlea (superior), Cranial Nerve: IV
6
Q
What is the function of the Inferior oblique muscle?
A
Rotates the eyeball on its horizontal axis temporally (Extorts and elevates the eye)
Origin: anterior nasal floor, Cranial Nerve: III
7
Q
Where do all extraocular muscles except the inferior oblique originate?
A
They originate from the orbital apex around the annulus of Zinn.
8
Q
What is the annulus of Zinn?
A
A fibrous ring that encircles the optic foramen.
9
Q
What muscles originate from the annulus of Zinn?
A
The four rectus muscles and the superior oblique.
10
Q
What does the trochlea do?
A
It redirects the superior oblique tendon.
11
Q
How do the rectus muscles move?
A
They move forward in a conal pattern, forming a muscle cone around the globe.
12
Q
Where do the rectus muscles insert?
A
They insert anterior to the globe’s equator, approximately 40 mm long.
13
Q
Describe the pathway of the superior oblique muscle.
A
It arises above the annulus of Zinn, becomes a tendon, passes through the trochlea, and inserts under the superior rectus.
14
Q
Where does the inferior oblique muscle originate?
A
It originates at the anterior nasal orbital floor.
15
Q
Where does the inferior oblique muscle insert?
A
It inserts inferior to the globe macula.
16
Q
What is the function of the arched pathway of the superior and inferior oblique muscles?
A
It allows torsional movements of the eye.
17
Q
What is the primary function of the levator palpebrae muscle?
A
It lifts the upper eyelid.
18
Q
What is the origin of the levator palpebrae?
A
Near the annulus of Zinn.
19
Q
Describe the course of the levator palpebrae.
A
It travels forward, superior, and slightly medial to the superior rectus.
20
Q
Where does the levator palpebrae insert?
A
It inserts into the upper eyelid.
21
Q
What is the anesthesia implication for the levator palpebrae?
A
Akinesia is not required because it retracts but does not contract around the globe.
22
Q
Does the levator palpebrae contribute to increased intraocular pressure (IOP)?
A
No, it does not contribute to increased IOP.
23
Q
What is the function of the orbicularis oculi muscle?
A
It contracts to close the eyelids.
24
Q
What are the divisions of the orbicularis oculi?
A
Orbital (outermost), palpebral (central layer), and tarsal (innermost).
25
How is the orbicularis oculi arranged?
In concentric rings around the eyelid.
26
What is the anesthesia implication for the orbicularis oculi?
Akinesia is typically desired to prevent involuntary eyelid movement and increased IOP due to contraction pressure around the globe.
27
What is the function of CN II (Optic)?
Vision (sensory).
## Footnote
Risk of CNS depression if anesthetic enters sheath.
28
What is the pathway of CN II (Optic)?
~25–30 mm long, runs from optic chiasm → optic canal → posterior globe.
## Footnote
S-shaped curve allows eye mobility.
29
What are the clinical notes regarding CN II (Optic)?
Injection into the optic nerve sheath can result in CNS depression or respiratory arrest via CSF spread.
## Footnote
Carries the central retinal artery and vein.
30
What is the function of CN III (Oculomotor)?
Motor (primary/most extraocular muscles), parasympathetic to pupil constrictors.
31
Which muscles does CN III (Oculomotor) innervate?
Superior rectus, Inferior rectus, Medial rectus, Inferior oblique, Levator palpebrae superioris (upper eyelid).
32
What are the parasympathetic fibers of CN III (Oculomotor)?
Synapse at ciliary ganglion → iris sphincter (pupil constriction).
33
What is the unique anatomy of CN IV (Trochlear)?
Only cranial motor nerve entering orbit outside the muscle cone.
## Footnote
Moves medially to reach its target.
34
What is the function of CN V (Trigeminal)?
Sensory (mainly) + some motor.
35
What are the branches of CN V (Trigeminal)?
V1 – Ophthalmic (sensory), V2 – Maxillary (sensory), V3 – Mandibular.
36
What does the ophthalmic branch of CN V (Trigeminal) supply?
Pain, touch, & temperature of lacrimal, frontal, cornea, conjunctiva, iris, eyelids, forehead, nose.
37
What is the function of CN VI (Abducens)?
Motor; Innervates lateral rectus.
38
What is the function of CN VII (Facial)?
Motor for muscles of the face; Innervates orbicularis oculi; motor component for eyelid closure.
39
What is the clinical note regarding CN VII (Facial)?
Blocking this nerve helps akinesia of eyelids during eye surgery.
40
What is the function of CN X (Vagus)?
Parasympathetic and motor (larynx, heart, viscera).
41
What is the clinical relevance of CN X (Vagus)?
Efferent limb of oculocardiac reflex (OCR).
## Footnote
Can cause bradycardia or dysrhythmia during eye traction or pressure.
42
What is the shape of the orbit?
The orbit is pear-shaped.
43
How do the medial walls of the orbit extend?
The medial walls extend straight back.
44
What is the angle between the lateral walls of the orbit?
The lateral walls diverge at a ~90-degree angle from each other.
45
What structures are contained in the apex of the orbit?
The apex contains the superior orbital fissure and inferior orbital fissure.
46
What is the function of the superior and inferior orbital fissures?
They are entry points for orbital nerves and vessels.
47
Where is the optic foramen located?
The optic foramen is located medial to the superior orbital fissure.
48
What passes through the optic foramen?
The optic nerve (CN II) and ophthalmic artery pass through the optic foramen.
49
What does the optic foramen connect?
It connects the intracranial space to the intraorbital space.
50
Where is the lacrimal bone located?
The lacrimal bone is located just behind the medial orbital rim.
51
What is the significance of the lacrimal bone?
It is a landmark for medial peribulbar block.
52
Where is the ethmoid bone located in relation to the lacrimal bone?
The ethmoid bone lies posterior to the lacrimal bone.
53
What is the first branch of the internal carotid artery?
The ophthalmic artery.
54
How does the ophthalmic artery enter the orbit?
It enters via the optic canal, usually inferolateral to the optic nerve.
55
What is the central retinal artery?
It enters the optic nerve 8–15 mm posterior to the globe.
56
What do the long and short posterior ciliary arteries supply?
They supply the choroid and optic nerve.
57
What does the supraorbital artery supply?
It supplies the forehead.
58
What does the lacrimal artery supply?
It supplies the lacrimal gland.
59
What does the dorsal nasal artery communicate with?
It communicates with the angular artery (external carotid system).
60
What is the origin of the infraorbital artery?
It is a branch of the external carotid system via the maxillary artery.
61
Where does the infraorbital artery travel?
It travels through the infraorbital canal and exits through the infraorbital foramen.
62
What is the primary venous drainage of the orbit?
The superior ophthalmic vein.
63
Where does the superior ophthalmic vein drain?
It drains into the cavernous sinus via the superior orbital fissure.
64
What does the inferior ophthalmic vein originate from?
It originates from a plexus on the orbital floor.
65
What does the central retinal vein drain into?
It drains directly into the cavernous sinus.
66
What is an important note about orbital veins?
Orbital veins are valveless; flow is pressure-dependent, increasing risk for retrograde infections or air embolism.
67
Which nerves enter the orbit through the superior orbital fissure outside the muscle cone?
Trochlear nerve (CN IV), Frontal nerve (branch of CN V1), Lacrimal nerve (branch of CN V1).
68
Which nerves enter the orbit through the superior orbital fissure inside the muscle cone?
Oculomotor nerve (CN III), Abducens nerve (CN VI), Nasociliary nerve (branch of CN V1).
69
What does the optic canal transmit?
The optic nerve (CN II) and ophthalmic artery.
70
What passes through the supraorbital notch?
The supraorbital nerve and artery.
71
What passes through the infraorbital foramen?
The infraorbital nerve and artery (branch of maxillary nerve CN V2).
72
What is the Muscle Cone?
Formed by rectus muscles around the optic nerve.
73
What is the Annulus of Zinn?
Fibrous ring at orbital apex; origin for most EOMs.
74
What is the function of the Trochlea?
Pulley for the superior oblique tendon.
75
What is the significance of the Lacrimal bone?
Landmark for medial peribulbar block.
76
What are the Supra/Infraorbital notches?
Exit points for respective sensory nerves.
77
What is the average total orbital volume?
~30 mL
## Footnote
Globe (eyeball): 6.5–7 mL; Remaining ~23 mL: Comprised of extraocular muscles, vessels, nerves, and orbital fat.
78
What is the average orbital depth?
~48 mm (range: 42–52 mm from infraorbital rim to optic foramen).
79
Where does the orbital floor end?
Does not reach orbital apex; ends around the posterior wall of the maxillary sinus (approximately two-thirds depth).
80
Where is orbital fat present?
Present in both intraconal and extraconal compartments.
81
What is the role of the orbital septum?
Fibrous anterior boundary preventing fat herniation.
82
What is the visual axis?
Line from midpoint of cornea to macula; used for intraocular lens alignment.
83
What is the normal axial length of the globe?
Normal: 23–23.5 mm.
84
What is the axial length of a hyperopic eye?
< 22 mm – may allow more space behind globe.
85
What is the axial length of a myopic eye?
> 24 mm – thinner sclera increases risk of globe puncture during needle blocks.
86
What should you ask if the axial length is unknown?
Ask about history of nearsightedness or retinal surgery.
87
What is Staphyloma?
Protrusion of uveal tissue through a weakened scleral wall.
## Footnote
Common in myopia; increases risk of globe rupture with needle-based regional anesthesia.
88
Where can Staphyloma be located?
Locations: Anterior, equatorial, or posterior.
89
What is the Tenon Capsule?
A fibrous connective tissue layer enveloping the eyeball, beginning near the corneal limbus and fused with the conjunctiva.
90
What are the functions of the Tenon Capsule?
Forms a sliding socket for eye movement within the orbit.
91
What is Orbital Connective Tissue?
A complex mesh of connective tissue septa that starts at the orbital apex and becomes more defined anteriorly.
92
What is the function of Orbital Connective Tissue?
Maintains the central position of the globe and limits its displacement during motion.
93
What are the Fascial Sheaths of Extraocular Muscles?
Intermuscular membranes that connect the sheaths of all four rectus muscles and anchor the muscles to the orbit.
94
What is the function of the Fascial Sheaths of Extraocular Muscles?
Enhances stability and alignment of muscles, improves efficiency of extraocular movement.
95
What is noted about the posterior orbit in relation to Fascial Sheaths?
Fascial sheaths are less distinct.
96
Is there a single 'common muscle cone' identified in the Fascial Sheaths?
No single 'common muscle cone' identified—each muscle sheath contributes to the fibrous meshwork.
97
What are common antibiotics used in ophthalmology?
Antibiotics are commonly used in ophthalmology.
98
What are mydriatics?
Mydriatics are drugs that dilate the pupil.
## Footnote
Example: phenylephrine
99
What are miotics?
Miotics are drugs that constrict the pupil.
## Footnote
Example: pilocarpine
100
What are cycloplegics?
Cycloplegics are drugs that paralyze the ciliary muscle.
## Footnote
Example: atropine
101
What types of anti-inflammatory drugs are used in ophthalmology?
Anti-inflammatory drugs include NSAIDs and steroids.
102
What are viscoelastics used for?
Viscoelastics are used in intraocular surgeries to protect ocular tissues.
103
What are common glaucoma therapies?
Glaucoma therapies include beta blockers and prostaglandin analogs.
104
How can medications enter systemic circulation from eye drops?
Medications can enter through the outer eye membrane and the lacrimal drainage system, which leads to the nasolacrimal duct, nasal mucosa, and then into the bloodstream.
105
What are strategies to reduce systemic absorption of eye drops?
Close eyes for 60 seconds post-instillation, avoid blinking, and apply gentle pressure to the medial canthus (punctal occlusion).
106
What does a metallic taste after eye drops indicate?
It may indicate systemic absorption, which requires vigilance.
107
What is topical/intraocular anesthesia commonly used for?
It is common in cataract surgery.
108
What is an example of topical anesthesia?
2% lidocaine drops or gel
## Footnote
Often supplemented with intracameral injection of preservative-free 1% lidocaine.
109
What are the advantages of topical/intraocular anesthesia?
Safe, simple, preserves motor function, and allows for rapid recovery.
110
What are the disadvantages of topical/intraocular anesthesia?
No akinesia and variable pain relief.
111
What is a Sub-Tenon block?
It provides deeper analgesia than topical anesthesia and is performed between the rectus muscles of the globe.
112
What is the procedure for a Sub-Tenon block?
Conjunctiva is incised, Tenon’s capsule is lifted and incised, a blunt cannula is inserted into the sub-Tenon space, and local anesthetic is injected.
113
What are the advantages of a Sub-Tenon block?
Good analgesia and safer than sharp needle blocks.
114
What are the limitations of a Sub-Tenon block?
Variable akinesia and requires more skill and time than topical.
115
What is the ocular regional needle block?
It is the most common and effective way to produce profound analgesia and akinesia.
116
Which cranial nerves are affected by ocular regional anesthesia?
CN III (oculomotor), IV (trochlear), V (trigeminal), VI (abducens), VII (facial).
117
Where is the ocular regional procedure performed?
In the orbital epidural space.
118
What is the needle used for a retrobulbar block?
A 23-gauge dull needle.
119
Where is the insertion site for a retrobulbar block?
In the infratemporal quadrant, just above the inferior orbital rim.
120
What is the needle trajectory for a retrobulbar block?
Advanced toward the orbital apex, 35 mm deep.
121
What is the typical anesthetic volume for a retrobulbar block?
2–4 mL injected into the muscle cone.
122
What should be done post-injection in a retrobulbar block?
Digital pressure is applied over the closed eyelid, and the globe is inspected for akinesia after a few minutes.
123
What are potential complications of ocular anesthesia?
Trauma to optic nerve, vessels, globe, seizures from inadvertent intravascular injection, and respiratory arrest if anesthetic enters CSF via optic nerve sheath.
124
What is the modified approach for gaze direction during needle insertion?
Use primary gaze (straight ahead) or down-and-out gaze to shift vital structures away.
125
What is the recommended needle depth to reduce optic nerve trauma?
Recommended depth: 19–25 mm – just posterior to globe, reduces optic nerve trauma.
126
What type of needles should be used for safer navigation?
Use dull/flat-grind needles, curved-tip, or pinhead needles for safer navigation.
127
How can patient comfort be improved during procedures?
Sedation or topical anesthetic may improve tolerance.
128
What is the current understanding of orbital anatomy?
Newer anatomical understanding emphasizes 360° fascial septa and open orbital communication.
129
What is the risk associated with the original needle angle approach?
Higher risk of trauma to optic nerve, vessels, and globe.
130
What is the advantage of the modified needle angle approach?
Lower risk to posterior structures; parallel path avoids optic nerve and vasculature.
131
What is the original needle depth and its associated risk?
Original depth: ~35 mm (1.38 in) → higher risk.
132
What is the modified needle depth and its benefit?
Modified depth: ~25 mm (1 in) → places needle just behind globe, avoiding deep orbital structures.
133
What is the safe range for needle depth?
Safe range: 19–31 mm (0.75–1.25 in), accounting for orbital and globe size variability.
134
What eye position is recommended to reduce risk during needle insertion?
Primary gaze or down-and-out maintains S-shaped optic nerve; reduces risk of trauma.
135
What is a Peribulbar Block?
A Peribulbar Block involves inserting a needle outside the muscle cone (extraconal) to create positive pressure, spreading anesthetic into the cone.
136
What is the volume used in a Peribulbar Block?
The volume used is larger, typically between 8–12 mL.
137
What cranial nerves are targeted in a Peribulbar Block?
The block targets anesthesia of cranial nerves III–VII.
138
What are the common injection sites for a Peribulbar Block?
Common injection sites include inferotemporal (most common), medial, or superior-temporal.
139
What is the safety advantage of a Peribulbar Block?
It has a lower risk of optic nerve injury and is safer for patients with conditions like high myopia, enophthalmos, staphyloma, or a history of scleral buckle.
140
What is a key note regarding Peribulbar blocks?
Peribulbar blocks may require repeat injections due to poor spread into the cone from extraconal sites.
141
How does axial length affect needle insertion in orbital procedures?
The axial length of the globe helps estimate when the needle passes the equator, typically at ~12.5 mm insertion.
142
What is the geometric method by Harvey?
It allows calculation of a safe redirection point based on the orbital-globe relationship.
143
What is the least vascular injection zone for retrobulbar and peribulbar blocks?
The inferotemporal zone is the most common and safest for these blocks.
144
What are key safety practices for needle insertion?
Use primary gaze or down-and-out positions, insert needle to ~25 mm depth, favor a parallel approach, and avoid deep needle paths unless necessary.
145
What is the purpose of the Gills-Lloyd Modified Retrobulbar Block?
It provides deep orbital anesthesia and akinesia with improved safety over the original Atkinson technique.
146
What is the needle insertion site for the Gills-Lloyd Modified Retrobulbar Block?
The insertion site is transconjunctival, inferotemporal, parallel to the lateral limbic margin (corneoscleral junction).
147
What is the depth for needle insertion in the Gills-Lloyd Modified Retrobulbar Block?
Insert the needle to 25 mm (1 inch) and redirect cephalad after passing the globe equator (~12.5 mm).
148
What is the volume/dose for the Gills-Lloyd Modified Retrobulbar Block?
Inject 1–1.5 mL of 1–2% lidocaine after negative aspiration, with a total of ~6 mL for orbital filling.
149
What are key technique highlights for the Gills-Lloyd Modified Retrobulbar Block?
Start with a small volume peribulbar injection, inject slowly (1 mL/10 sec), and monitor for pressure sensation.
150
What are the advantages of the Gills-Lloyd Modified Retrobulbar Block?
It avoids optic nerve and vessels, is safer than traditional retrobulbar, and can provide globe and eyelid akinesia without a separate CN VII block.
151
What is the purpose of Peribulbar Extraconal Block Techniques?
Safer block option for high-risk patients (e.g., long axial length, staphylomas, previous scleral surgery).
152
Where are the injection sites for Peribulbar Extraconal Block?
Inferotemporal and/or supraorbital regions for better anesthetic spread.
## Footnote
Medial peribulbar block for eyelid akinesia or missed muscle targets.
153
What is the needle insertion technique for Peribulbar Extraconal Block?
Insert 25 mm (1 inch) needle outside the muscle cone, directed parallel to or angled away from visual axis.
154
What is the recommended volume for Peribulbar Extraconal Block?
Large volume 10–12 mL (e.g., 6 mL inferior, 4–6 mL superior).
155
What is the technique summary for Infraorbital injection?
Inject lateral to limbic margin, bevel toward globe.
156
What is the technique summary for Supraorbital injection?
Insert just inferior to supraorbital rim (12 o'clock).
157
What should be done after the block for drug spread?
Apply positive pressure after block for drug spread and IOP control.
158
How long should you wait for anesthesia to set in?
Wait 10 minutes for anesthesia to set in.
159
What are the limitations of Peribulbar Extraconal Block?
May not achieve full akinesia due to septal barriers; requires multiple injection sites or repeat blocks.
160
What is the purpose of the Medial Peribulbar Block?
Primary or supplemental block, especially useful for eyelid akinesia (CN VII).
161
Where is the needle site for Medial Peribulbar Block?
Insert through caruncle conjunctiva, angled toward lacrimal bone.
162
What is the needle length for Medial Peribulbar Block?
Use 0.5-inch (12 mm) needle; avoid the puncta, canaliculi, and medial rectus muscle.
163
What is the recommended volume for Medial Peribulbar Block?
Inject ~3 mL or more after negative aspiration.
164
What are the advantages of the Medial Peribulbar Block?
Provides eyelid akinesia with less discomfort than Van Lint or Nadbath blocks; can be used alone or to supplement incomplete globe akinesia; avoids deep injection and globe trauma.
165
How is ocular block evaluation performed?
Akinesia of globe is evaluated:
- Retrobulbar block: ~2 minutes post-injection.
- Peribulbar block: ~10 minutes post-injection.
166
What should be assessed during ocular block evaluation?
Globe movement in all four quadrants should be assessed; eyelid movement: if orbicular muscle still active, supplement with medial peribulbar block.
167
What is the purpose of the Orbicularis Oculi Block?
It is a supplemental block when eyelid movement remains after retrobulbar or peribulbar anesthesia.
168
How is the Inferotemporal injection performed for the Orbicularis Oculi Block?
Insert a 30-gauge, 0.5-in needle bevel down, tangential to the skin. Inject 1–2 mL of local anesthetic subcutaneously and digitally spread to medial and lateral canthi.
169
What is the technique for the Supranasal injection in the Orbicularis Oculi Block?
Use the same needle placement, depress the globe with finger pressure, inject 1–2 mL bevel down, tangential to the lid, and digitally spread followed by light pressure to prevent bleeding.
170
What does the Van Lint Technique provide?
It provides akinesia of the orbicular muscle (eyelids) via facial nerve (CN VII) branches.
171
What is the needle gauge and length used in the Van Lint Technique?
Use a 25–27 gauge, 1.5-in needle.
172
What are the steps for the first and second injections in the Van Lint Technique?
First injection: inferotemporal, 1–2 mL along the lower orbital rim, then withdraw. Second injection: redirect supratemporally along upper orbital rim with 1–2 mL.
173
What is the issue with Positive Orbital Pressure & Chemosis?
Retrobulbar/peribulbar blocks increase orbital volume, which may increase intraocular pressure (IOP) and cause chemosis (subconjunctival edema).
174
How can Positive Orbital Pressure & Chemosis be prevented or managed?
Use positive-pressure devices to reduce IOP, enhance anesthetic spread, and normalize orbital anatomy before surgery.
175
What is the Honan Intraocular Pressure Reducer?
It is a pneumatic compression cuff used after ocular blocks.
176
What is the technique for using the Honan Intraocular Pressure Reducer?
Tape the eye shut, place folded 4x4 gauze over the eye, secure the Honan cuff over gauze with Velcro head strap, and inflate pressure to 30 mm Hg.
177
What effect does the Honan Intraocular Pressure Reducer have?
It deepens the anterior chamber and reduces IOP for safer surgery.
178
What should be assessed in young children preoperatively for eye surgery?
Assess for congenital, metabolic, and musculoskeletal abnormalities (e.g., malignant hyperthermia).
179
What should be evaluated in elderly patients preoperatively for eye surgery?
Evaluate for polypharmacy, multisystem disease, and drug interactions.
180
What are key day-of-surgery considerations for anesthesia management?
Stress reduction is critical; use a kind demeanor, hypnotic techniques, and progressive relaxation.
181
What should be included in the pre-op assessment for eye surgery?
Review mental/physical status, vital signs, ECG, and postpone surgery if any new significant findings are observed.
182
What should be evaluated before planning anesthesia for regional versus general anesthesia?
Evaluate for claustrophobia, severe arthritis, tremors, restless leg syndrome, and physical limitations that impair lying supine.
183
What should elderly patients bring on the day of surgery?
Patients should bring their medication list or bottles.
184
What is essential for final anesthesia clearance?
It should be a collaborative decision between the anesthesia provider and the attending ophthalmologist on the day of surgery.
185
When should general anesthesia be considered?
General anesthesia should be considered for infants and young children, patients with severe claustrophobia, uncontrolled acute anxiety or panic attacks, inability to cooperate, communicate, or lie still, and surgical procedures expected to last more than 2 hours.
186
What is the preferred anesthesia technique for adults and elderly patients?
Regional anesthesia is usually well tolerated by most adults and should be the preferred technique in adults and elderly patients when appropriate, due to the lower systemic risks.
187
What are the permissive NPO policies before ocular surgery?
Permissive protocols include allowing a light breakfast for morning surgery, a light lunch for afternoon surgery, and clear fluids permitted until admission.
188
What are the strict NPO protocols before ocular surgery?
Strict protocols may still be applied at some institutions.
189
What are the preoperative medication instructions for patients?
Patients should continue home medications unless directed otherwise. Diuretics may be held in patients with frequent urination complaints.
190
What should be done with antiglycemic agents when a patient is NPO?
Antiglycemic agents (oral hypoglycemics or insulin) may need to be reduced or withheld when NPO.
191
What is the threshold for acute increased intraocular pressure (IOP)?
Sudden IOP ≥ 40 mm Hg can result in ocular content expulsion.
192
What are the causes of acute increased intraocular pressure?
Coughing and choroidal hemorrhage.
193
What is the mechanism behind the spike in IOP during acute increased intraocular pressure?
Elevated intrathoracic pressure → venous backflow in valveless orbital veins → IOP spike.
194
What happens during choroidal hemorrhage?
Blood fills the choroid, leading to a rapid rise in IOP.
195
What can happen if pressure is not controlled quickly during choroidal hemorrhage?
It may disrupt the globe unless pressure is controlled quickly.
196
Are IOP-lowering medications effective in the acute phases of choroidal hemorrhage?
IOP-lowering meds may be ineffective in acute phases.
197
Why is coughing a concern for patients with increased IOP?
The risk of coughing increases IOP and compromises globe integrity.
198
What are some prevention strategies for coughing in patients with increased IOP?
Vasoconstrictive nasal drops for postnasal drip, small sips of water for dry throat, instruct patients to warn staff before coughing, encourage throat clearing over forceful coughing, promote shallow breathing.
199
What may blunt the cough reflex in patients with increased IOP?
IV lidocaine or sedation may blunt cough reflex but are less effective once cough starts.
200
What happens to patients after surgery regarding transport and observation?
Patients are transferred to the Postanesthesia Recovery Unit (PAR).
201
What factors influence recovery time after surgery?
Mental and physical condition, amount of sedation or anesthesia used.
202
What are the advantages of regional anesthesia for ambulatory procedures?
Less pain, lower rates of postoperative nausea, shorter recovery times.
203
What is postoperative nausea (PONV)?
May occur immediately post-op.
204
What are common causes of postoperative nausea?
Sedation medications, elevated IOP, ocular pain.
205
What is more likely to cause at-home nausea later in the day?
Increased IOP, not medications.
206
What are the preoperative preparation steps for general anesthesia in ophthalmic surgery?
Follow appropriate fasting guidelines based on age and comorbidities. Remind patients that the operative eye will be patched upon awakening. Sedation as needed to reduce anxiety, with midazolam effective in low doses. Use multimodal antiemetic strategies to minimize postoperative nausea and vomiting (PONV).
207
What agents are recommended for induction and maintenance in ophthalmic surgery?
Propofol or etomidate are recommended as both reduce intraocular pressure (IOP). Inhalation induction is preferred for infants and young children, also helping to reduce IOP.
208
What is the recommended narcotic use during ophthalmic surgery?
Use narcotics in low doses due to the risk of nausea/emesis.
209
What airway management is typically required for ophthalmic procedures?
Most procedures (except short ones) require endotracheal intubation or laryngeal mask airway (LMA).
210
What are the effects of succinylcholine on intraocular pressure (IOP)?
Succinylcholine increases IOP transiently, peaking at +9 mm Hg at 6 minutes, but is still considered safe for ophthalmic use.
211
What are the caveats of using succinylcholine in eye muscle surgery?
Sustained contraction may interfere with the forced duction test, and there is a theoretical risk of expulsion with open globe, though no confirmed human cases.
212
What are alternative muscle relaxants to succinylcholine?
Nondepolarizing agents decrease IOP and provide satisfactory intubating conditions.
213
How can the IOP response be attenuated during laryngoscopy?
Laryngoscopy with light anesthesia increases IOP; pre-treat with IV lidocaine (1.5–2 mg/kg) 1–1.5 min before.
214
What are the special considerations for intraocular procedures?
Traction on orbital structures may trigger the oculocardiac reflex, requiring continuous ECG monitoring. Eye muscle surgery is associated with malignant hyperthermia and postoperative nausea. In retinal procedures involving intraocular gas, discontinue nitrous oxide 15 min before injection.
215
What are the strategies for extubation and airway management?
After return of spontaneous breathing and reversal of NMB, extubate under deep anesthesia with 100% oxygen and position the patient laterally until fully awake.
216
What should be done in difficult cases during extubation?
For full stomach, difficult airway, or incompetent LES, perform gastric suction and administer IV lidocaine (1.5–2 mg/kg) before extubation.
217
What are the advantages of using a laryngeal mask airway (LMA)?
Can be inserted without muscle relaxants and may be removed in an awake patient with less coughing.
218
What are the risks associated with LMA?
Limited airway access intraoperatively, malposition or dislodgement, and laryngospasm or coughing if anesthesia is too light.
219
What are common uses of LMA in ophthalmic surgery?
Commonly used in strabismus surgery and scleral buckle procedures.
220
What is the focus of postoperative care in ophthalmic surgery?
Focus on pain control, PONV prevention, and maintaining stable IOP. Notify ophthalmologist if there is persistent nausea, as it may signal increased IOP.
221
What are the priorities in managing traumatic open-globe injuries?
Emergencies requiring general anesthesia prioritize preventing aspiration and avoiding IOP increases to reduce the risk of globe rupture.
222
What is the normal range for Intraocular Pressure (IOP)?
Normal IOP is 10–22 mm Hg.
223
What factors affect Intraocular Pressure (IOP)?
IOP is affected by aqueous humor production/elimination, choroidal blood volume, CVP, and extraocular muscle tone.
224
Where is aqueous humor produced?
Aqueous humor is produced in the ciliary body.
225
What is the pathway of aqueous humor flow?
Aqueous humor flows from the posterior chamber → around the iris → to the anterior chamber.
226
How does aqueous humor drain?
It drains through the canal of Schlemm into the episcleral veins.
227
What factors can increase Intraocular Pressure (IOP)?
Factors include venous congestion (coughing, Valsalva, head-down tilt) and mydriatics (which decrease drainage through spaces of Fontana).
228
What are the theories behind succinylcholine's effect on IOP?
Mechanism theories include tonic muscle contraction, choroidal vasodilation, and elevated CVP.
229
How does IOP increase compare with other factors?
IOP increases more with crying, Valsalva, blinking, rubbing eyes, and coughing.
230
What are preoperative patient risk factors for ophthalmic anesthesia complications?
Anxiety and cardiovascular disease may provoke severe hypertension, cardiac dysrhythmias, and angina before surgery. Vasovagal responses, such as syncope, are common due to anxiety and can be managed effectively with ammonia capsules.
231
What chronic conditions must be addressed preoperatively?
Chronic coughing from COPD, asthma, and postnasal drip must be addressed preoperatively.
## Footnote
Use vasoconstrictive nose drops for postnasal drip and encourage coughing/deep breathing to clear mucus, reducing both systemic and ocular complications.
232
What are common causes of complications in regional ocular blocks?
Most adverse events are due to orbital vessel trauma, globe trauma, optic nerve trauma, and patient movement during both regional and general anesthesia.
233
What is the cause of retrobulbar hemorrhage?
Direct trauma to orbital vessels during block.
234
What are the clinical presentations of retrobulbar hemorrhage?
Proptosis, subconjunctival hemorrhage, eyelid/orbital ecchymosis, and pressure in the orbit that may occlude central retinal artery or vein, potentially causing vision loss.
235
What are the onset types of retrobulbar hemorrhage?
Venous hemorrhage has a gradual onset, while arterial hemorrhage has a rapid and pronounced onset.
236
How is retrobulbar hemorrhage detected?
Noted by progressive orbital pressure on palpation; continuous digital pressure may halt venous bleeding.
237
What is the management for persistent pressure in retrobulbar hemorrhage?
Perform lateral canthotomy immediately, which may be done by an anesthetist or ophthalmologist, who must be notified.
238
What is the goal of a lateral canthotomy?
To expand orbital space and reduce pressure to prevent vision loss.
239
What is localized episcleral hemorrhage?
Subconjunctival bleeding without proptosis, usually from local anesthetic spread. Notify ophthalmologist before surgery.
240
What is the epidemiology of retrobulbar hemorrhage?
It is the most common complication of ocular blocks, occurring in 1% to 3% of all regional blocks, and is seen in both retrobulbar and peribulbar techniques.
241
What are the causative agents for seizures after retrobulbar injections?
Seizures have been reported after injections using lidocaine, lidocaine-bupivacaine combinations, and ropivacaine.
242
What mechanism can trigger seizures during retrobulbar injections?
Even subtoxic doses may cause seizures if injected intraarterially, as retrograde arterial flow can send the anesthetic to cerebral circulation.
243
What does the Mathers survey suggest about seizure incidence in ophthalmology?
Out of 200 surveyed ophthalmologists, 66 responded, and 3 reported seizures following retrobulbar blocks, suggesting underreporting in the literature.
244
What reactions may occur from orbital vein injection?
Shivering and rigor within 15 seconds, with symptoms typically resolving in approximately 2 minutes.
245
What are the risk factors for globe puncture?
Globe puncture can occur with either sharp or dull needles and has been reported even by experienced practitioners.
246
When may globe puncture be diagnosed?
Diagnosis can occur 1–14 days post-injection.
247
What is the most severe outcome of globe puncture?
Ocular explosion, which is the rupture of the globe due to elevated intraocular pressure from injection.
248
What are high-risk patient characteristics for globe puncture?
Axial length greater than 24 mm (myopic eye), scleral buckling, staphyloma, enophthalmos, and supranasal gaze.
249
What increases the risk of globe puncture?
Multiple orbital injections and unexpected patient movement.
250
What is the debate regarding needle safety in ocular injections?
Blunt needles are not proven safer and can still cause optic nerve trauma, globe penetration, and CNS complications. Notify the surgeon immediately if globe puncture is suspected.
251
What are the components of the optic nerve sheath?
The optic nerve sheaths are extensions of brain meninges, consisting of an outer sheath (dura mater) and inner layers (arachnoid and pia mater).
252
What does the subarachnoid space contain?
Cerebrospinal fluid (CSF) and is continuous with the optic chiasm.
253
What happens at the optic foramen regarding the dura mater?
The dura splits into an outer layer (orbital periosteum) and an inner layer (optic nerve sheath).
254
What can happen with inadvertent injection into the subdural/subarachnoid space?
It can track to the optic chiasm or brainstem, resulting in contralateral amaurosis, cranial nerve III dysfunction, and respiratory arrest.
255
What clinical clue indicates potential subarachnoid or subdural spread?
If the contralateral pupil is constricted pre-block and then dilates post-block.
256
What is the onset time for respiratory arrest after an injection?
Onset is typically 2–5 minutes but may be delayed up to 10–17 minutes.
257
What is the recovery time for respiratory arrest?
Spontaneous breathing may return in 15–20 minutes, while full neurologic recovery may take up to 55 minutes.
258
What are the immediate supportive measures for respiratory arrest?
Airway support and ventilation, supplemental oxygen, continuous ECG and BP monitoring, and notifying the ophthalmologist immediately.
259
What other considerations are there regarding retrobulbar hemorrhage?
It may also compress the central retinal artery/vein, and direct trauma from the needle can cause vascular occlusion without hemorrhage.
260
What equipment is needed for the Canthotomy procedure?
1 straight hemostat and 1 plastic scissors
261
What is the first step in the Canthotomy procedure?
If possible, inject lidocaine along the lateral canthus
262
What is the second step in the Canthotomy procedure?
Place hemostat in a temporal direction along lateral canthus (4–6 mm) and clamp
263
What is the third step in the Canthotomy procedure?
Remove the hemostat
264
What is the fourth step in the Canthotomy procedure?
Use plastic scissors to incise only in crush marks left by the hemostat
265
What is the fifth step in the Canthotomy procedure?
Control local bleeding with hemostat or digital pressure
266
What measures can prevent retrobulbar hemorrhage?
Choose least vascular areas for needle placement, avoid deep orbital injections, avoid supranasal position of gaze, use primary gaze position, use upward-gaze position (Gills-Lloyd technique only), insert needle slowly
267
What measures can prevent seizures from intravascular injection?
Choose least vascular areas for needle placement, avoid deep orbital injections, avoid supranasal position of gaze, insert needle slowly, aspirate gently before injection, avoid injection against resistance, avoid forceful rapid injections
268
What measures can prevent globe puncture?
Use caution in patients with increased axial length, avoid supranasal position of gaze, direct needle away from the axis of the globe during insertion through orbital septum, observe globe movement with needle insertion, insert needle slowly with bevel toward the globe, never forcefully inject anesthetic, use modified retrobulbar and peribulbar techniques
269
What are the signs and symptoms of globe puncture?
Increased resistance to injection, immediate dilation and paralysis of the pupil, rapid increase in IOP with edematous cornea, hypotony of the globe, intraocular hemorrhage. Patient may or may not exhibit signs and symptoms immediately.
270
What measures can prevent optic nerve sheath trauma?
Avoid supranasal eye position, avoid deep orbital injection, insert needle slowly, avoid forceful injection of anesthetics, use modified retrobulbar or peribulbar techniques.
271
What measures can prevent extraocular muscle trauma?
Avoid needle contact with extraocular muscles, avoid deep orbital penetration, avoid angling needle toward visual axis of the globe when parallel to an extraocular muscle.
272
What are the prevention and treatment measures for complications from the Nadbath block?
Avoid using the Nadbath technique in patients weighing <45 kg, avoid using large volumes of anesthesia and hyaluronidase, avoid using the Nadbath technique when patients have a preexisting unilateral vocal cord dysfunction, place the patient in seated or lateral position to maintain a patent airway and patient comfort, the patient with an unsatisfactory airway should be intubated.
273
What are the complications of ocular ischemia?
Retinal vascular occlusion or thrombosis has been reported after ocular blocks. Decreased pulsatile ocular blood flow may occur due to the pressure from local anesthetic volume, not always associated with a significant rise in IOP.
274
What risk considerations should be taken for ocular blocks?
Use caution in patients with compromised ocular circulation. Some clinicians recommend avoiding epinephrine in local anesthetic solutions.
275
What is optic nerve atrophy?
Optic nerve atrophy may occur after intraocular surgery, regardless of anesthesia type (regional or general).
276
What are the potential results of direct trauma to the optic nerve?
Direct trauma to the optic nerve may result in transient contralateral amaurosis, respiratory arrest, or partial or complete vision loss from vascular occlusion or thrombosis.
277
What is inferior rectus muscle palsy?
Inferior rectus muscle palsy is reported after retrobulbar anesthesia and not observed after general anesthesia.
278
What are the findings associated with inferior rectus muscle palsy?
Segmental enlargement of the inferior rectus muscle located posterior to the globe.
279
What symptoms are associated with inferior rectus muscle palsy?
Symptoms include vertical diplopia, often persistent, and may require surgical correction.
280
What trauma is associated with superior oblique tendon-trochlea?
Superior oblique tendon-trochlea trauma is reported following peribulbar anesthesia.
281
What did Carlson et al. find regarding muscle study?
Minimal myotoxicity observed from retrobulbar injections; surface fibers degenerate and regenerate, while direct injection into rectus muscle leads to massive internal damage and functional deficit.
282
What clinical effects can local anesthetic myotoxicity lead to?
Local anesthetic myotoxicity may lead to postoperative diplopia and ptosis. Elderly patients are at higher risk due to impaired muscle regeneration.
283
What are other causes of ptosis?
Other causes of ptosis include age-related changes, superior rectus stay suture, eyelid speculum trauma, and may take up to 6 months for resolution.
284
What are common patient complaints from facial nerve blocks?
Discomfort from cranial nerve VII (facial nerve) blocks.
285
What complications are associated with facial nerve blocks?
Prolonged Bell palsy reported with Nadbath technique and O’Brien technique, likely due to direct trauma to CN VII.
286
What are serious adverse effects of facial nerve blocks?
Serious adverse effects include dysphagia, hoarseness, cough, and respiratory distress caused by unintended spread of anesthetic to vagus nerve (CN X), glossopharyngeal nerve (CN IX), and spinal accessory nerve (CN XI).
287
What is noted about the location of certain cranial nerves?
These nerves exit the skull ~10 mm medial to CN VII.
288
What other observations have been made regarding facial nerve blocks?
Jaw pain reported for weeks after Nadbath block. Rare seizure reported with 3 mL of 2% lidocaine + epinephrine 1:200,000 during Nadbath block.
289
What was documented in the needle injury case report by Zaturansky and Hyams?
Documented ocular perforation during modified Van Lint block; needle penetrated globe just beneath insertion of lateral rectus muscle.
290
What is the Oculocardiac Reflex?
It is a trigeminal–vagal reflex that can be triggered by various stimuli.
291
What are common stimuli for the Oculocardiac Reflex?
Pressure on the globe, orbital structures, conjunctiva, and traction on extraocular muscles, especially the medial rectus.
292
What are the afferent neural pathways involved in the Oculocardiac Reflex?
Long/short ciliary nerves → Ciliary ganglion → Gasserian ganglion → Ophthalmic division of the trigeminal nerve → Trigeminal sensory nucleus (in floor of 4th ventricle).
293
What are the efferent neural pathways involved in the Oculocardiac Reflex?
Vagus nerve → Cardioinhibitory center.
294
What clinical occurrences may trigger the Oculocardiac Reflex?
Local infiltration, retrobulbar or peribulbar block, and general anesthesia. It is more common in pediatric muscle surgeries.
295
What are the cardiac dysrhythmias associated with the Oculocardiac Reflex?
Acute sinus bradycardia, nodal rhythms, AV block, ventricular ectopy, idioventricular rhythm, and asystole.
296
What is essential for monitoring during the Oculocardiac Reflex?
Continuous ECG monitoring is essential.
297
What are the management steps for the Oculocardiac Reflex?
1. Ask surgeon to stop stimulation. 2. Assess oxygenation, ventilation, and anesthetic depth. 3. Dysrhythmia may resolve spontaneously. 4. If unresolved, administer IV atropine (2–3 mg for full vagal blockade) or consider glycopyrrolate for milder cases. 5. Surgeon may resume once rhythm stabilizes. 6. If reflex recurs, repeat process. 7. Reflex fatigues with repeated stimulation. 8. Pre-treatment with atropine or glycopyrrolate may help, especially in children.
298
What is the most common ocular injury from general anesthesia?
Corneal abrasion.
299
What causes corneal abrasion during general anesthesia?
Corneal drying and direct trauma (e.g., mask injury).
300
How can corneal abrasion be prevented?
Ensure eyelids are closed and taped.
301
What is the most frequent cause of surgical complications?
Movement during surgery.
302
What causes movement during surgery?
Coughing and bucking, commonly due to inadequate muscle relaxants or no nerve stimulation.
303
What causes chemical injury during surgery?
Prep solution spills.
304
How should chemical injury be managed?
Flush with saline immediately.
305
What can improper patient positioning lead to?
Central retinal artery occlusion, especially in prone cases.
306
How can improper patient positioning be prevented?
Use adequate padding, perform periodic eye checks, and use eye protection (e.g., foam headrests, gel donuts).
307
What should be done if a patient reports symptoms post-op?
Request an ophthalmology consult.
308
What are the challenges in ophthalmic anesthesia?
Complex comorbidities, multiple pharmacologic interactions in the elderly, and pediatric-specific airway and respiratory risks (e.g., chronic URIs).
309
What is a trend in ophthalmic anesthesia for cataracts?
Topical anesthesia is becoming common.
310
What is increasing the demand for regional blocks in ophthalmic surgery?
Advances in retinal surgery, corneal transplants, adult strabismus, and glaucoma surgery.
311
What are the benefits of orbital regional blocks?
Less postoperative pain, reduced need for opioids, and reduced PONV.
312
When is general anesthesia still preferred?
For children, trauma patients, and patients not suited for regional/topical anesthesia.
