Ophthalmic Procedures

Question 2

A characteristic feature of postoperative visual loss due to posterior ischaemic optic
neuropathy is:

a) Painful
b) Normal light reflexes
c) Normal fundoscopy
d) Visual inattention

Answer 2

c) Normal fundoscopy

Question 3

21.1 The most common cause of postoperative visual loss after spinal surgery is

a. Central retinal artery occlusion
b. Central retinal vein occlusion
c. Ischemic optic neuropathy
d. Haemorrhage
e. corneal abrasion

Answer 3

c. Ischemic optic neuropathy

Cardiac: Anterior
Spinal: Posterior
ION

Question 4

19.1, 20.1 Soon after a peribulbar block, the patient’s eye rapidly becomes proptosed and tense, and the visual acuity is markedly decreased. A lateral canthotomy is indicated to:

a) Allow globe to continue to swell
b) Drain blood from behind eyeball
c) Allow the eye to proptose
d) Reduce pressure on the optic nerve

Answer 4

c) Allow the eye to proptose

Orbital Compartment Syndrome

The orbital compartment is a fixed space with limited capacity for expansion. If something like blood fills part of that space the pressure increases and may result in ischaemia of the optic nerve or the retina. A lateral canthotomy is a way of releasing this pressure.

You have up to approximately 2 hours before irreversible visual loss occurs. It may occur in less than 2 hours however, so speed is of the essence.

use local anesthetic but warn the patient that they may feel pain

Perform the canthotomy:
place the scissors across the lateral canthus and incise the canthus full thickness

Perform cantholysis:
Grasp the lateral lower eyelid with toothed forcepsPull the lower eyelid anteriorlyPoint the scissors toward the patient’s nose, place the blades either side of the lateral canthal tendon, and cut.

By cutting the canthal tendon,the counter pressure of the eyelid on the is relieved and the eye is allowed to proptose and pressure is relieved.

Question 5

21.2 Stellate ganglion block is NOT contraindicated in patients with

a) Contralateral phrenic nerve palsy
b) Glaucoma
c) Recent MI
d) Arrhythmia

Answer 5

d) Arrhythmia
- caution if conduction disease however

Contraindications are current coagulopathy (or anticoagulated), recent myocardial infarction, pathologic bradycardia, and glaucoma.

Source Radiopaedia

Contralateral stellate ganglion/phrenic nerve block/neuropathy

Question 6

20.1, 22.2 Your patient underwent a stellate ganglion block 2 hours ago. Prior to discharge you are asked to review the patient in recovery because of a droopy upper eyelid. The patient would also be expected to have ipsilateral

a) Pupillary constriction and reaction to light
b) Pupillary constriction and no response to light
c) Pupillary dilation and response to light
d) Pupillary dilation and no response to light

Answer 6

a) Pupillary constriction and reaction to light

Stellate ganglion block causes ipsilateral Horner’s Syndrome:
Ptosis (eyelid droop)
Miosis (constricted pupils)
Anhydrosis (loss of sweating)
Enophthalmos (sinking of eyeball into the bony cavity that protects the eye)
*Pupillary constriction in response to light is controlled by the Edinger-Westphal nucleus of CN3, which will remain intact.

Question 7

21.2 Suxamethonium causes a sustained contraction of the extraocular muscles for up to

a) 2 minutes
b) 3 minutes
c) 5 minutes
d) 10 minutes
e) 20 minutes

Answer 7

d) 10 minutes
- best answer; one of those shit questions that depends on your source.

Morgan & Mikhail’s (chapter 36: anaesthesia for ophthalmic surgery):
“ Succinylcholine increases IOP by 5-10mmHg for 5-10 minutes”.
- due to prolonged contracture of the EOM

BARASH:
Succinylcholine increases IOP 7 to 10 mmHg reaching a peak pressure 1 to 2 minutes after IV administration and returns to the baseline in 5 to 7 minutes. This increase may be attenuated by pretreatment with anesthetics, although none completely eliminates the increase in IOP. In the presence of a lacerated globe, this increase in IOP may increase the extrusion of intraocular contents although greater increases in IOP may occur during crying and coughing.

Yao & Artusio’s:
- also quotes same information: increases IOP 7 to 10mmHg, returning to baseline in 5 - 7 minutes.

Stoelting’s:
Intraoccular pressure peaks at 2-4 minutes after administration and returns to normal by 6 minutes

Question 8

22.1 A patient has undergone a multilevel cervical spine fusion and upon emergence from anaesthesia reports complete visual loss. Fundoscopic examination shows a pale optic disc with haemorrhages. This supports a diagnosis of

a. CRAO
b. AION
c. PION

Answer 8

Ischaemic optic neuropathy (anterior)

https://www.researchgate.net/figure/Top-Funduscopic-examination-revealed-pale-and-swollen-discs-with-small-hemorrhages-on_fig2_6759964

Question 9

21.1 Sensory innervation of the cornea is by the

A. Ophthalmic division of the Trigeminal nerve
B. Nasocilliary Nerve
C. Frontal Nerve
D. Oculomotor

Answer 9

B. Nasocilliary Nerve
a branch of Ophthalmic division of trigeminal

Question 10

20.2 The most common cause of post operative visual loss after spinal surgery is

a) Corneal abrasion
b) Retinal artery occlusion
c) Central retinal vein occlusion
d) Ischaemic optic neuropathy
e) Occipital infarct

Answer 10

a) Ischaemic optic neuropathy

Postoperative visual loss (POVL) occurs in 1/60 000–1/125 000 operations. Spinal surgery has the highest incidence of POVL.

American Society of Anesthesiologists (ASA) Post Operative Visual Loss Registry, spinal surgery accounted for 93/131 (70%) of all cases of visual loss after non-ophthalmic surgery.
Of these:
> 83 were attributable to ischaemic optic atrophy (ION)
> 10 were caused by central retinal artery occlusion (CRAO).

CRAO
- caused by direct pressure on the globe causing raised intraocular pressure and compromising retinal perfusion.
- visual loss is usually unilateral and associated with other signs of pressure (e.g. ophthalmoplegia, ptosis, or altered sensation in the territory of the supraorbital nerve).
- Initial careful positioning of the head and regular checks throughout the procedure in case of movement minimizes the risk
- documentation of eye checks should occur every 30mins and horseshoe shaped head rests should be avoided in prone patients

ION
> associated with:
- male gender
- obesity
- increasing blood loss
- operative procedures >6 hrs in length.
- The use of the Wilson frame has also been implicated.
> final common pathway is thought to be hypoperfusion of the optic nerve, there is no clear association with either intraoperative systemic hypotension or with the presence of peripheral vascular disease or diabetes.
> recently updated ASA practice advisory for POVL associated with spinal surgery recommends regular intraoperative testing of haemoglobin concentration. However, it was unable to suggest a transfusion threshold that would prevent POVL.

Other possible causes of POVL:
1. Cortical ischaemia
2. Haemorrhage into a cerebral tumour.

In high-risk cases, assessment of vision should be performed as soon as possible in PACU and an early ophthalmic opinion sought if there is a suggestion of visual compromise.

Initial management
1. optimization of arterial pressure
2. oxygenation
3. correction of anaemia.

Treatment with agents such as acetazolamide has not been beneficial and there is rarely any useful improvement in vision with either injury, so attention should be focused on preventative measures:
1. Careful positioning with the head at the same level as the heart
2. Meticulous haemostasis,
3. Possibly staging prolonged procedures should be considered.

Because of the devastating nature of this complication, patients should be informed of an increased incidence of visual loss after spinal operations that are expected to be of prolonged duration and associated with significant blood loss.

Question 11

22.1 You are planning to perform a peribulbar block and wish to check the axial length of the eye prior to proceeding. The average axial length of the globe in adults as measured by ultrasound is

a. 20mm
b. 23mm
c. 26mm
d. 29mm
e. 32mm

Answer 11

B 23mm

Question 12

22.2 The normal axial length of the globe of an adult eye is
a. 20mm
b. 23mm
c. 26mm
d. 29mm
e. 32mm

Answer 12

23mm

Question 13

21.2 Techniques to improve the speed of onset and spread of a peribulbar block include all of the
following EXCEPT

a) Honan balloon
b) Digital pressure
c) Ocular massage
d) Hyalase

Answer 13

c) Ocular massage

Hyalase
Mixing with lignocaine
Higher concentration
Higher volume
Occular pressure (spread and IOP reduction)

Source: 2x BJA Ed articles

Question 14

21.2 The medical laser LEAST likely to cause eye injury is

a) CO2
b) Nd:YAG
c) Argon
d) Green light

Answer 14

CO2

Laser danger is proportional to penetration.
Penetration inversely proportional to the laser wavelength.

CO2 laser has very little penetration (~ 10micrometres), as it has a wavelength of 10 600nm.
Helium-Neon laser also has very little penetration.

Nd:YAG is the most powerful, with a penetration of 2-6mm, as it has a wavelength of 1064nm.

Question 15

21.2 The oculocardiac reflex results in

a) Hypertension
b) Apnoea
c) Junctional rhythm
d) Torsades

Answer 15

c) Junctional rhythm

Up to date: Anaesthesia for elective eye surgery

Oculocardiac reflex manifestations —
Manifestations of the oculocardiac reflex commonly occur when pressure is applied to extraocular muscles.
These include bradycardia (a decrease of 10 to 20 percent in the basal heart rate), junctional rhythms, hypotension, and, rarely, asystole.
This reflex can occur during injection of local anesthesia or during the surgical procedure itself.
Management includes stopping the stimulus (eg, release of traction or manipulation of the extraocular muscles).
If this is ineffective, an anticholinergic medication (eg, atropine or glycopyrrolate) is administered.
The risk of inducing this reflex may be reduced by an effective regional anesthetic block or general anesthesia with adequate depth.

Question 16

23.1 A 72-year-old woman on aspirin therapy presents to her ophthalmologist for follow up three days after you performed a transconjunctival peribulbar block for cataract surgery on her left eye. She complains of painless periorbital swelling, erythema and mild chemosis which started the day after surgery but is improving. She also had a peribulbar block three weeks ago for surgery on the other eye. The most likely diagnosis is

a. Retrobulbar haemorrhage
b. Residual swelling from peribulbar block
c. Periorbital cellulitis
d. Hyalase/hyaluronidase reaction/allergy
E. Conjunctivitis

Answer 16

d. Hyalase/hyaluronidase reaction/allergy

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4850816/

Question 17

21.2 Painless post-operative visual loss with preserved pupillary reflexes is most likely due to

a) Retinal detachment
b) Anterior ischaemic optic neuropathy
c) Corneal abrasion
d) Posterior ischaemic optic neuropathy
e) Posterior cerebral ischaemia

Answer 17

PCA

e) Posterior cerebral ischaemia

UTD: Postoperative visual loss after anaesthesia for nonocular surgery

Pupillary light reflexes*
Unilateral central retinal artery occlusion, ischemic optic neuropathy, and retrobulbar hematoma result in a poor or absent pupillary response to light (“direct” response) with a normal response when light is directed to the other pupil (“indirect” response); this “relative afferent pupillary defect” is revealed when tested with the swinging flashlight maneuver; if these processes are bilateral, there will be poor or absent direct pupillary responses and a relative afferent pupillary defect only if asymmetric.
Mid-dilated and nonreactive pupils are consistent with acute angle-closure glaucoma, while sluggish to fixed and dilated pupils are seen with glycine-induced visual loss.
Pupillary light reflexes are normal in cases of corneal abrasion, cerebral or cortical visual loss, and in cases of PRES. Examination of pupils is discussed more fully separately.

Question 18

21.1 Globe perforation during eye block is more common in myopic eyes because

a) Higher rate of increased IOP
b) Globe is too short
c) Incidence of staphyloma
d) Corneal thickness is less

Answer 18

c) Incidence of staphyloma

But also reduced space between globe and orbit

Axial eye length: implications for globe perforation during regional block –

• The axial length of the eye (distance from the cornea to the retina) is routinely measured by ultrasound before cataract surgery to determine the proper intraocular lens size to be implanted.
• It has been noted that patients with long eyes (axial length >25 mm) have an increased risk of needle injury during a retrobulbar (intraconal) block, usually due to penetration of the posterior pole of the globe.
• Indications that the eye may be longer than average include a history of myopia in childhood (confirmed by an affirmative answer to the question, “Did the patient need to wear glasses as a child to see distant objects?”) or the presence of globe-enveloping intraorbital hardware, such as a scleral buckle.
• Also, patients with an abnormal outpouching of the eye called a staphyloma, which is usually associated with an axial length >25 mm and is usually located in the posterior portion of the globe, are at increased risk for globe perforation by a retrobulbar needle
• In such patients, retrobulbar block is usually avoided in favor of a peribulbar (extraconal) or sub-Tenon block, topical anesthesia, or general anesthesia.

Question 19

23.1 A patient you anaesthetised for a cervical fusion reports rapidly progressing unilateral visual loss commencing two days postoperatively. Fundoscopic examination reveals optic disc oedema. The most likely diagnosis is

A. AION
B. PION
C. CRAO
D. Vertebrobasilar stroke
E. Retinal detachment

Answer 19

A. AION

Answer is more likely ‘A - Anterior Ischaemic Optic Neuropathy, because:
1. Most common
2. One or two days post - up to 12
3. Optic disc oedema (CRAO - fundoscopic appearance is that retina appears pale with cherry red central spot). PION fundoscopy is normal at first but has late developing oedema. It is less common than AION.

https://eyewiki.aao.org/Non-Arteritic_Anterior_Ischemic_Optic_Neuropathy_(NAION)

As mentioned earlier, optic disc edema is always present in the acute phase of NAION (the reason will be discussed in the section under Pathophysiology) and comes in two varieties, diffuse or segmental.

Posterior ischemic optic neuropathy (PION) encompasses those conditions that result in ischemia to any portion of the optic nerve posterior to the optic disc. By definition, PION will not cause disc edema.

Symptoms:
The classic description of patients with NAION presenting with acute, painless unilateral vision loss that is often described as a blurring or cloudiness of vision, often inferiorly, has been expanded. Although the majority of patients do not have accompanying pain, headache or periocular pain is reported in 8-12% of patients, which can make it difficult to differentiate from optic neuritis

Question 20

22.2 A 72-year-old woman on aspirin presents to her ophthalmologist for follow-up three days after you performed a transconjunctival peribulbar block for cataract surgery on her left eye. She complains of painless periorbital swelling, erythema, and mild chemosis which started the day after surgery but is improving. She had a peribulbar block three weeks ago for surgery on the other eye. The most likely diagnosis is

a. Retrobulbar bleeding?
b. Residual swelling from peribulbar block
c. Infection
d. hyalase reaction/allergy

Answer 20

d. hyalase reaction/allergy

Question 21

20.2 Features indicating an arterial retrobulbar haemorrhage sustained during a peribulbar eyeblock administered for cataract surgery include all of the following EXCEPT

a) Chemosis
b) Proptosis
c) Decreased visual acuity
d) Increased intraocular pressure

Answer 21

Chemosis is NOT a sign of arterial retrobulbar haemorrhage

Signs of arterial retrobulbar haemorrhage:
1. Sudden onset proptosis
2. Raised IOP
3. Reduced acuity.

Question 22

22.1 The most common cause of bilateral blindness following spinal surgery and anaesthesia is

a. Ischaemic optic neuropathy
b. Retinal artery occlusion
c. Retinal detachment
d. Cortical stroke

Answer 22

ION
Post - spinal
Ant - cardiac

repeat

Question 23

Characteristics of post-operative visual loss due to vertebrobasilar ischaemia include

a) inattention
b) Vision returns in 24hrs
c) relevant afferent pupillary defect
d) diplopia

Answer 23

d) diplopia

Bilateral visual loss associated with insufficiency to posterior circulation so: parieto-occipital ischaemia, signs of stroke, visual agnosia, ophthalmoplegia or diplopia.

Question 24

A relative contraindication to a peribulbar needle technique for cataract surgery is:

a) Axial length of 24mm
b) INR 2.5 for mechanical aortic valve
c) Staphyloma
d) Scleral buckle
e) Pterygium

Answer 24

c) Staphyloma

https://eyewiki.aao.org/Ocular_Anesthesia#cite_note-:2-3

Contraindications

Absolute
Confirmed allergy to a necessary anesthetic, and nystagmus. Other contraindications are just those of the particular surgery that is to be performed.

Relative
Long eye (in the anterior to posterior axis, evidenced by high myopia), staphyloma (abnormal protrusion at a weak spot in the wall of the eye), enophthalmos (posteriorly or deep set eyes), and extended surgery duration are relative contraindications to retrobulbar and peribulbar anesthesia. In an uncooperative patient, patients deemed to be unable to follow commands during surgery, children and those with uncontrollable neurological movements, general anesthesia may be considered.

Question 25

This patient has been requested to look straight ahead. He is suffering from a right

a) Horner’s Syndrome
b) 3rd nerve palsy
c) 4th nerve palsy
d) 6th nerve palsy

Answer 25

b) 3rd nerve palsy

https://derangedphysiology.com/main/required-reading/neurology-and-neurosurgery/Chapter%204631/lesions-oculomotor-nerve-cn-iii
This is the “down and out” eye syndrome. It is characterised by ptosis, a down-and-out pupil, mydriasis, absent light reflex with intact consensual constriction of the opposite eye, and failure of accommodation. Classically, this is the lesion which develops during uncal herneation, due to an ipsilateral cerebral injury.

Causes of unilateral CN III lesions:
- Uncal herneation: Pressure from herniating uncus on nerve
- Fracture involving ipsilateral cavernous sinus
- Cavernous sinus thrombosis (ipsilateral)
- Aneurysm (ipsilateral)
- Midbrain lesion (see Question 26.2 from the second paper of 2011)

Causes of bilateral CN III lesions:
- Cavernous sinus thrombosis
- Aneurysm
- Contralateral brainstem lesion (midbrain)

Exclusion of a 4th nerve lesion
- Tilt the head to the same side as the lesion
- The affected eye will intort if the fourth nerve is intact.