Week 2 - Eyes Flashcards
(106 cards)
1
Q
What are the four main goals of anesthesia in ophthalmic surgery?
A
Patient safety; Providing analgesia to elicit a pain-free experience and create optimal surgical conditions; Minimizing risks during anesthesia and sedation; Managing potential outcomes associated with eye surgeries.
2
Q
Which extraocular muscle is located at the 12 o’clock position and moves the eye upward?
A
Superior rectus
3
Q
Which extraocular muscle is located at the 6 o’clock position and moves the eye downward?
A
Inferior rectus
4
Q
Which extraocular muscle is located medially to the 12 o’clock position and adducts the eye?
A
Medial rectus
5
Q
Which extraocular muscle is located laterally to the 12 o’clock position and abducts the eye?
A
Lateral rectus
6
Q
Which extraocular muscle is located on the superior aspect of the eye and intorts and depresses the eyeball?
A
Superior oblique
7
Q
Which extraocular muscle is located on the inferior aspect of the eye and extorts and elevates the eyeball?
A
Inferior oblique
8
Q
What is the function and innervation of the superior rectus muscle?
A
Function: Supraduction
Cranial Nerve: CN III (Oculomotor)
9
Q
What is the function and innervation of the inferior rectus muscle?
A
Function: Infraduction
Cranial Nerve: CN III (Oculomotor)
10
Q
What is the function and innervation of the medial rectus muscle?
A
Function: Adduction
Cranial Nerve: CN III (Oculomotor)
11
Q
What is the function and innervation of the lateral rectus muscle?
A
Function: Abduction
Cranial Nerve: CN VI (Abducens)
12
Q
What is the function and innervation of the superior oblique muscle?
A
Function: Intorsion-depression
Cranial Nerve: CN IV (Trochlear)
13
Q
What is the function and innervation of the inferior oblique muscle?
A
Function: Extorsion-elevation
Cranial Nerve: CN III (Oculomotor)
14
Q
What is the primary muscle responsible for raising the upper eyelids?
A
Levator muscle of the upper eyelid
15
Q
Which muscle causes eyelid contraction and has 3 divisions?
A
Orbicularis oculi (orbicular muscle of the eye); divisions: orbital, palpebral, tarsal
16
Q
Which cranial nerve supplies the orbital portion?
A
Cranial Nerve II (Optic nerve), not a true cranial nerve, it’s an outgrowth of the brain
17
Q
What is the shape of the orbital fossa?
A
Pear shaped
18
Q
What is the usual volume of the orbit and the volume of a typical globe?
A
Orbit: 30 mL
Globe: 6.5–7 mL
19
Q
What is the procedure of cataract extraction ?
A
It involves removing the cloudy lens and replacing it with a plastic intraocular lens (IOL).
20
Q
What is a cataract and why is it significant?
A
A cataract is the opacification of the crystalline lens and is the leading cause of treatable blindness in the world.
21
Q
What are the two main techniques for cataract extraction?
A
Extracapsular technique and Intracapsular technique.
22
Q
What does the extracapsular technique involve?
A
Removal of the crystalline lens through an anterior lens capsule opening (capsulectomy), leaving the posterior capsule intact.
23
Q
How is the lens nucleus removed in extracapsular extraction?
A
Through an 8–10 mm incision or by phacoemulsification using ultrasound energy to aspirate fragmented lens material.
Advantage of phacoemulsification: small incision (3 mm), reducing trauma
Both approach allow the removal of cortical lens material by aspiration which leaves the posterior capsular bag intact to support an IOL implant.
24
Q
What happens if the lens capsule cannot support an IOL?
A
The lens can be sutured in the posterior chamber, or an anterior chamber IOL can be placed in front of the iris.
25
What are common materials used for intraocular lenses (IOLs)?
Polymethylmethacrylate, silicon, and acrylic.
26
What is the advantage of silicon and acrylic IOLs?
They are foldable and can be inserted through a small incision, making them most commonly used.
27
How is the wound closed after cataract surgery?
With nylon or Vicryl suture for a watertight seal; small incisions are often self-sealing and may not require sutures.
28
What does the intracapsular technique involve and differ from extracapsular technique?
Removal of the crystalline lens with its surrounding capsular bag intact (the whole thing is removed)
29
What must be done to the zonules during an intracapsular procedure?
The zonules ( The zonules that normally stabilize and
center the lens) must be broken to destabilize the lens and allow removal
30
What tool is often used to remove the lens during intracapsular extraction?
A cryoprobe is often used to extract the lens through a large incision
31
Why is the intracapsular technique performed infrequently?
* Because extracapsular techniques offer superior visual outcomes.
* The intracapsular technique may be used when capsular bag support is compromised due to trauma or inherited disorders
32
proper control of IOP crucial during what intraocular surgeries?
It is crucial for procedures such as glaucoma drainage surgery, open sky vitrectomy, penetrating keratoplasty, and traditional intracapsular cataract extraction.
33
What kinda of IOP do we want before scleral incision?
LOW-NORMAL IOP is what we want, because abrupt decompression of a hypertensive eye could result in iris or lens prolapse, vitreous loss, or expulsive choroidal hemorrhage.
34
State 2 important things we want for intraocular surgery?
* Complete akinesia
* Maximal pupillary dilation
35
How is akinesia achieved during intraocular surgery?
Nondepolarizing drugs are administered followed by neuromuscular function monitoring to ensure 90–95% twitch suppression during surgery.
36
How can pupillary dilation be induced during intraocular surgery?
By continuous infusion of epinephrine 1:200,000 in a balanced salt solution, delivered through a small-gauge needle placed in the anterior chamber.
37
What is glaucoma?
A condition characterized by elevated IOP resulting in impairment of capillary blood flow to the optic nerve with eventual loss of optic nerve tissue and function
38
What are the two anatomic types of glaucoma?
Open-angle and closed-angle
39
What defines open-angle glaucoma?
The elevated IOP exists with an anatomically open anterior chamber angle
40
What defines closed-angle glaucoma?
The peripheral iris moves into direct contact with the posterior corneal surface, mechanically obstructing aqueous humor outflow
41
What is the most common surgical procedure used to reduce IOP after failed medical therapy?
Trabeculectomy
42
Explain the steps in trabeculectomy
* A drainage fistula is made to allow aqueous humor to flow from the anterior chamber to the subconjunctival space.
* Incisions are made in the conjunctiva and Tenon’s layer to expose the sclera, followed by creating a partial-thickness scleral flap (hinged at the limbus).
* A sclerotomy is performed by removing a small piece of tissue from the base of the flap.
* An iridectomy is done to prevent the iris from blocking the fistula and protect against future angle closure
* The scleral flap is then closed with sutures.
43
What is the ultimate aim of retinal surgery?
Preservation or recovery of vision through the restoration of normal posterior segment anatomy
44
What procedures may be included in retinal surgery?
Involves various procedures alone or in combination: Scleral buckling, vitrectomy, gas-fluid exchange, injection of vitreous substitutes
45
What are scleral buckles and their purpose?
Silicone rubber appliances sutured to the sclera to indent the eye wall, relieve vitreous traction, and functionally close retinal tears
Scleral buckles can be done as an external procedure with a small needle puncture through the sclera for drainage of subretinal fluid or not entered at all
46
What are used frequently in retinal surgery and why?
* Cryotherapy or lasers. To establish chorioretinal adhesions around tears
47
How is cryotherapy and lasers applied in retinal surgery?
* Cryotherapy applied to the sclera
* laser is applied via fiber optic cable into the vitreous cavity during vitrectomy
48
How do we fix simple retinal detachments?
Can be fixed by a pneumatic retinopexy - where tears are treated with cryotherapy/laser and expanding gas is injected into the vitreous cavity
This technique is usually done in phakic eyes (with intact lenses) with tears between 9 and 4 o’clock positions
49
What is the purpose of vitrectomy in retinal surgery?
To reduce traction on the retina, clear blood and debris, and remove scar tissue
50
How is a vitrectomy performed?
* With three 20–25 gauge openings made in the vitreous cavity
* Involves 3 small incisions (20–25 gauge) into the vitreous cavity using a myringotomy blade 3–4 mm posterior to the limbus.
* Inferotemporal incision infuses balanced salt solution.
* Other incisions allow for a hand-held fiber optic light and surgical instruments (manual or automated).
* Visualization of the retina during the vitrectomy aided by a contact lens, which is either sutured to the eye or held in position by an assistant.
* Balanced salt solution replaces removed vitreous.
* Gas bubble may be added for tamponade of retinal tears.
* May also use liquid vitreous substitutes (e.g., perfluorocarbon liquids or silicone oil).
51
What are two types of vitreous substitutes used during vitrectomy?
**Perfluorocarbon liquids or silicone oil**
*** Perfluorocarbon liquids:**
Heavier than water, used intraoperatively to flatten (unfold) the detached retina.
Useful in reattaching giant retinal tears in supine position and faciliate reattaching the retina when PVR is present.
*** Silicone oil:**
Used for complex cases needing long-term tamponade to prevent redetachment.
52
Lasers are used to treat a wide spectrum of eye conditions. What are some examples?
Including diabetic retinopathy, glaucoma, and age-related macular degeneration
53
What types of lasers are commonly used for ophthalmic surgery?
Argon, krypton, diode, dye-tuned, neodymium, and excimer lasers
54
What are the characteristics and uses of the argon laser?
* Emits blue-green light with a wavelength of approximately 488–515 nm.
* Light is strongly absorbed by hemoglobin, melanin, and other pigments.
* Useful in retinal detachment surgery to photocoagulate or cauterize pigment epithelium and the adjacent neurosensory retina.
* Creates an adhesion between the retina and the 'wall of the eye' to keep the retina attached.
* Achieves its effect by focal and controlled necrosis of a limited amount of ischemic retina.
* Also used with some efficacy to treat late complications in the natural history of retinal vein occlusion.
55
How does the YAG laser emits light? and is useful in which surgical context and why?
* The Yag laser emits light in the infrared range
* Useful in posterior lens-capsule surgery, because it has high-power density and is efficacious in creating an opening in opacified posterior capsule membranes. These membranes develop in 1/3 of cases after phacoemulsification or other extra capsular cataract surgery.
56
What is an excimer laser and what is its use in ophthalmology?
A high-power ultraviolet chemical laser. Frequently used in delicate refractive surgery (LASIK), also called laser corrective surgery.
57
What gases and mechanisms does an excimer laser use to produce laser light?
Uses a combination of inert gas and a reactive gas. Under electrical stimulation, a pseudomolecule called a dimer is generated. The dimer exists only in an energized state and emits laser light in the ultraviolet range.
58
How does the excimer laser remove tissue?
Supplies enough energy to disrupt molecular bonds of surface tissue through ablation, allowing removal of exceptionally fine layers of surface material with almost no heating or change to neighboring tissue.
59
What is a ruptured globe and how does it occur?
A ruptured globe involves a tear of either the corneal or scleral layers of the eye and can occur in the setting of blunt, penetrating, or perforating trauma.
60
What is the primary goal of surgical repair in globe rupture?
To replace extruded intraocular contents, close defects, and remove any foreign body.
61
When does complete examination of the eye happen after trauma?
* often delayed until the patient is in the OR.
* To reduce the risk of causing further damage, complete examination is delayed until the patient is in the controlled setting of the OR under general anesthesia.
62
How are anterior vs. posterior injuries managed in globe rupture?
Anterior injuries are easily identifiable. Posterior injuries may require extensive exploration, including 360-degree conjunctival opening and isolation of each extraocular muscle to inspect the entire scleral surface.
63
What type of sutures are used for corneal and scleral lacerations?
Corneal lacerations are usually closed with 10-0 nylon sutures; 8-0 nylon or Vicryl may be used for scleral tissue.
64
What triggers the oculocardiac reflex?
* Pressure on the globe and by traction on the extraocular muscles and the conjunctiva or the orbital structures
* By performance of a retrobulbar block, ocular trauma, and direct pressure on tissue remaining in the orbital apex after enucleation
* May appear during either local or general anesthesia; hypercarbia, hypoxemia, and inappropriate anesthetic depth augment incidence and severity
65
What are the afferent and efferent limbs of the oculocardiac reflex?
The afferent limb is trigeminal and the efferent limb is vagal
66
What is the most common manifestation of the oculocardiac reflex?
* Sinus bradycardia is the most common
* other dysrhythmias include junctional rhythm, ectopic atrial rhythm, atrioventricular blockade, ventricular bigeminy, multifocal premature ventricular contractions, wandering pacemaker, idioventricular rhythm, asystole, and ventricular tachycardia
67
What reduces the incidence of the oculocardiac reflex?
IV atropine given within 30 minutes of surgery
68
What is strabismus and what are its possible associations?
Idiopathic disorder that may be associated with poor vision, cataracts, trauma, neuromuscular disorders, or congenital syndromes
69
What is the goal of strabismus surgery and how is it performed?
To correct ocular misalignment; surgical correction involves isolation of one or more extraocular muscles with either recession (transection and reinsertion) or resection (shortening) of the muscle.
70
What is the prevalence of strabismus and its clinical relevance?
Strabismus has a prevalence of 3–5% in the pediatric population and is the most common pediatric eye surgery performed
71
What should be assessed preoperatively regarding patient positioning?
* Assess if the patient can lie flat for the entire procedure.
* GA may be required for those with chronic cough or difficulty lying flat (e.g., arthritis).
* Evaluate exercise tolerance and arthritic limitations.
* Thoroughly discuss the procedure to address patient concerns.
72
When might general anesthesia (GA) be required?
GA may be required for those with chronic cough or difficulty lying flat (e.g., arthritis).
73
What is important to discuss with the patient preoperatively?
Thoroughly discuss the procedure to address patient concerns.
74
What is the goal with monitored anesthesia care (MAC)?
Patient should be awake, comfortable, still, and cooperative for 1–2 hours.
75
What should be considered for patients with a ruptured/lacerated globe?
Patients may also have full stomachs if injury occurred <8 hrs after last meal.
76
What should be ruled out in cases of a ruptured globe?
A ruptured globe may be one of several injuries; rule out additional trauma.
77
What type of anesthesia is most commonly used for adult eye surgeries?
Most adult eye surgeries use regional anesthesia; children usually require general anesthesia.
78
What is key in monitoring during procedures?
Verbal communication is key even with standard monitors.
79
What type of anesthesia is often used for short ophthalmic procedures?
Often done with topical/regional anesthesia under MAC due to minimal blood loss.
80
What should be avoided to prevent surgical injury?
Avoid coughing/bucking—most common cause of surgical injury and poor outcomes.
81
Are atropine and neostigmine safe for glaucoma patients?
Yes, they are safe for glaucoma patients (minimal effect on pupil size/IOP).
82
What safety measure should personnel take when using lasers?
Personnel should wear goggles.
83
When is regional anesthesia contraindicated?
Regional anesthesia is contraindicated in open-eye injuries (↑ risk due to IOP).
84
What is common after strabismus surgery?
Postop vomiting is common after strabismus surgery.
85
What types of anesthesia techniques are used in ophthalmic surgery?
MAC, topical anesthesia (by ophthalmologist), regional (retrobulbar block, peribulbar block, sub Tenon’s block)
86
What are the key details (gauge? eye position, how to confirm needle position, how much to inject, what nerve block required to prevent eyelid movement and how much inject where, most common complication, and risk?) of a **retrobulbar block?**
* Approach from the infratemporal quadrant using a 25- or 27-gauge needle.
* Eye should be in neutral or downward and medial position.
* Inject 3–5 mL of anesthetic slowly after confirming no blood or CSF.
* Facial nerve block required to prevent eyelid movement (inject 4–8 mL above and below lateral orbit).
* Most common complication: hematoma (minimized with needle <31 mm).
* Other risks: local anesthetic toxicity, oculocardiac reflex, apnea, obtundation.
87
What are the key details (where to inject and how ml, gauges, onset compared to retrobulbar, adverse outcome) of a **peribulbar block**?
Inject 5–6 mL of anesthetic superior to the inferior orbital rim at the junction of the lateral and middle third of the lower lid.
Uses 25- or 27-gauge needle.
Slower onset than retrobulbar.
More likely to cause conjunctival swelling that may interfere with surgery.
88
What are the key details (gauge, volume, location of needle, onset, complications?) of a **sub Tenon’s block?**
Injection via 22-gauge cannula into the space below Tenon’s capsule.
Produces anesthesia similar to retrobulbar block.
Slower onset, less reliable akinesia;
inject 3–5 mL, may require more.
Complications are extremely rare.
89
What need to be done during pre-induction?
* **Midazolam** 1–2 mg IV for anxiolysis.
* Decrease IOP (intraocular pressure) pre-retinal reattachment surgery using: **Acetazolamide or Mannitol.**
* **Avoid narcotics** pre-op to reduce nausea/emesis.
* **Provide a thorough explanation of surgical events** to the patient.
* **Metoclopramide** 10 mg IV may aid gastric emptying in obese, anxious, or high-aspiration-risk patients.
90
What is the standard practice during induction regarding facial pressure?
Standard care should avoid putting pressure on the affected eye with the face mask
91
What is the induction strategy for repair of a ruptured or lacerated globe?
* **Use RSI with cricoid pressure** to protect the airway and decrease IOP
* **Preoxygenate** and avoid external eye pressure from the face mask
* Pretreat with a **nondepolarizing relaxant** followed by **IV lidocaine** and **fentanyl**
* Induce with **propofol** and **succinylcholine**; intubate with oral **RAE tube**
* In **pediatrics**: consider **sevoflurane** for induction while maintaining cricoid pressure and intubating after deep anesthesia
92
What is the induction approach for strabismus surgery?
* Use a vagolytic dose of **atropine** (0.02 mg/kg) or **glycopyrrolate** (0.01 mg/kg)
* **Sevoflurane** as an inhalation agent reduces oculocardiac and oculorespiratory reflexes
* **Forced duction test **(FDT) may be performed before muscle relaxants
* **Neuromuscular blockers** (NMB) may be used afterward to assist with ET intubation
93
What are the general anesthesia maintenance strategies for ophthalmic surgery? what to avoid and why?
Standard maintenance or TIVA; avoid hypercapnia which increases intraocular pressure (IOP)
94
What maintenance techniques can be used for strabismus surgery?
Techniques can include either inhalation agents or TIVA
95
What is the most effective approach to preventing PONV during strabismus surgery?
Combination therapy with drugs from different antiemetic drug classes
96
How does N₂O affect PONV risk during ophthalmic surgery?
The use of N₂O may increase the risk for postoperative nausea and vomiting (PONV)
97
What are the key considerations during anesthesia emergence for ophthalmic surgery?
* Decompress the stomach with an **OG tube**
* Administer intraoperative antiemetics **30 minutes before the end of surgery**
* **Deep extubation** may be requested by the surgeon in pediatric strabismus cases
98
What is the general approach to postoperative and pain management in ophthalmic surgery?
Continue acetaminophen and antiemetics as needed; occasional need for opioid analgesics
99
What are the 5 most important considerations in postoperative care?
* PONV is common → give metoclopramide 10 mg IV and ondansetron 4 mg IV 30 min before end of surgery.
* IV lidocaine, posterior pharyngeal suctioning, and a small amount of narcotic may blunt cough reflex before extubation.
* Avoid hypercapnia as it increases IOP.
* Humidify gases for pediatric patients.
* If GA risk is unacceptably high, use topical anesthesia for surgical repair.
100
What are the anesthesia-related concerns for strabismus repair?
Oculocardiac reflex, oculogastric reflex, forced duction testing, malignant hyperthermia
101
What are the anesthesia-related concerns for intraocular surgery?
Proper control of IOP, akinesia, drug interactions, associated systemic disease
102
What are the anesthesia-related concerns for retinal detachment surgery?
* Nitrous oxide interaction with air, sulfur hexafluoride, or perfluorocarbon gas bubble
* Venous air embolism, oculocardiac reflex, proper control of IOP
103
What are common complications associated with ophthalmic anesthesia?
Retrobulbar hemorrhage, Intravascular injection, Globe puncture, Optic nerve sheath trauma, Ocular ischemia, Extraocular muscle palsy & ptosis, Facial nerve blocks, Oculocardiac reflex
104
What is the most common injury after general anesthesia?
Corneal abrasion
105
What causes corneal abrasion under general anesthesia?
Drying of the exposed cornea or direct trauma (e.g., from an anesthesia mask)
106
How can corneal abrasion be prevented during general anesthesia?
Ensure eyelids are closed and secured with tape to protect the cornea
