This document discusses anaesthesia considerations for ophthalmology surgery. It begins with the anatomy of the eye and nerve supply. It then discusses various types of eye surgeries and choices of anaesthesia, including regional blocks and general anaesthesia. Key issues are managing intraocular pressure, the oculocardiac reflex, drug effects, and risks with nitrous oxide and anticoagulants. Factors that increase or decrease intraocular pressure during surgery are outlined. The document provides guidance on reducing pressure and handling reflexes to ensure safe ophthalmic anaesthesia.

1. ANAESTHESIA FOR
OPHTHALMOLOGY SURGERY
1
DR NOR HIDAYAH ZAINOOL ABIDIN

2. CONTENT
• Anatomy of the eyes
– Nerve supply
• Types of surgery
• Choice of Anaesthesia
• Problems associated with
ophthalmic surgery
- Intraocular pressure
- Oculocardiac reflex
- Systemic Effects of
ophthalmic drug
- Use of nitrous oxide
- Anti-coagulant
- Penetrating eye injury
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3. Nerve supply
• The optic nerve (CN II) carries the
neural signals from the retina.
• Touch and pain sensation is carried
via the trigeminal nerve (CN V).
– Sensation to the lower lid is via the
maxillary nerve.
– Sensation to the upper lid is via the
frontal branch of the ophthalmic nerve.
– The nasociliary branch of the
ophthalmic nerve sends sensory fibers
to medial canthus, lacrimal sac, and
ciliary ganglion.
3
• The oculomotor (CN III), trochlear
(CN IV), and Abducens (CN VI)
control the extraocular muscles.
(LR6, SO4)

4. • The ciliary ganglion (receive parasympathetic fibers from EW nucleus)
provides sensory innervation to the cornea, iris, and ciliary body.
– Spincter pupillae muscle (affecting pupil constriction)
– Ciliary muscle (affecting accomodation)
• Parasympathetic fibers originate from the oculomotor nerve (CN III) and
synapse in the ciliary ganglion before supplying the iris sphincter muscle.
• Sympathetic fibers originate from the carotid plexus and travel through
the ciliary ganglion to innervate the dilator muscle of the iris.
4
• The facial nerve (CN VII) exits the
base of the skull from the
stylomastoid foramen.
– motor innervation to the orbicularis
muscle via the zygomatic branch.

5. TYPES OF SURGERY
• Anterior segment surgery
- cataract extraction –lens implant
- glaucoma surgery
- corneal surgery-corneal transplant
• Posterior segment surgery
- retinal detachment surgery
- vitrectomy
• Strabismus surgery
• Lacrimal surgery
- dacryocystorhinotomy (DCR)
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• Orbital surgery
- enucleation, evisceration
• Ophthalmic oncology
- retinoblastoma
- uveal melanoma
• Ocular trauma
- penetrating eye injury
- T &S of corneal laceration

6. Emergency Eye Surgery
True Emergencies
•Therapy should be started within minutes for chemical burns
of the cornea and central retinal artery occlusion.
Urgent Situations
•Therapy should be started in 1 to several hours.
•Open-globe injuries, endophthalmitis, acute narrow-angle
glaucoma, acute retinal detachment, corneal foreign body,
and lid laceration.
Semi-urgent Situations
•Therapy should be started within days, but sometimes can be
rescheduled for several weeks.
•Ocular tumors, blow-out fractures of the orbit, congenital
cataract, and chronic retinal detachment.
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7. PROBLEMS-RELATED WITH OPHTHALMIC
SURGERY
• Extreme of age
- very young
- very old
• Control of intraocular pressure (IOP)
• Management of oculocardiac reflex
• Systemic effect of ophthalmic drugs
• Use of nitrous oxide in retinal detachment surgery
• Penetrating injury
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8. CHOICE OF ANAESTHESIA
SELECTION OF TYPE OF ANAESTHETIC
 Most paediatric patients require GA.
 In adults the prime determinant is often duration and nature of surgery.
 Anterior segment work < 2 hours  retrobulbar block.
 Retinal surgery usually GA.
Preference of the surgeon is important.
1. Regional anaesthesia
-Retrobulbar block
-Peribulbar block
-Facial nerve block
-Sub-Tenon block
2. General anaesthesia
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9. REGIONAL ANAESTHESIA
Advantages
• May be performed as day cases
• Awake patient
• Avoid complication of GA
• Produce good akinesia and
anaesthesia
• Minimal influence on intraocular
presssure
• Reduce post op nausea &
vomiting
• Early ambulation & recovery
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Disadvantages
• Not suitable for children
• Need patient cooperation
• Risk of inadequate analgesic
• Not suitable for some patients
(children, mentally handicapped,
deaf, language barrier)
• Not suitable for long procedure

10. REGIONAL ANAESTHESIA
LA is not always safer than GA - complications of block include:
 Retrobulbar haemorrhage - higher incidence with retrobulbar blocks
~1.4%
 Perforation of the globe:
Diagnosis of perforation- pain at the time the block is performed, sudden
loss of vision, hypotonia, a poor red reflex or vitreous hemorrhage.
 Stimulation of OculoCardiac reflex
 Puncture of posterior globe
 Optic nerve atrophy
- Optic nerve damage and retinal vascular occlusion may be caused by
direct damage to the optic nerve or central retinal artery, injection into
the optic nerve sheath or haemorrhage within the nerve sheath.
 IV injection of LA
 Subdural injection
- due to either direct injection into the dural cuff which accompanies the
optic nerve to the sclera or to retrograde arterial spread.
- symptoms : drowsiness, vomiting, contra-lateral blindness caused by
reflux of the drug to the optic chiasma, convulsions, respiratory
depression or arrest, neurological deficit, and even cardiac arrest.
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11. Feature of Retrobulbar block
• Relatively easy
• Single injection
• Small volume of LA needed
• High success rate
• Rapid onset (within 5 minute)
• Complete akinesia
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12. Feature of peribulbar block
• Two injection needed
• Large amount of LA needed
• Onset is slower (15-30 min)
• Less likely to perforate sclera
12

13. Compare Retrobulbar block and peribulbar
block
Retrobulbar block Peribulbar Block
Advantage More denser, akinesia of
extraocular muscles
- Easier, less risk of complication
- The potential for intraoacular
and intradural injection is
decreases because LA is
deposited outside the muscle
cone
Disadvantage Challenging, risky
Higher risk of retrobulbar
haemorhage and perforationnof
eye or injury to optic nerve
- Less dense block
- Greater volume required
- More time required for
satisfactory block
- Higher incidence of periorbital
ecchymosis and conjuctival
chemosis
Similarity - Both blates oculocardiac reflex by blocking afferent
- Block ciliary ganglion (V1), CN 3, 6; do not block CN7 (need extra
facial block), CN4 might be blocked by diffusion.
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14. Sub-Tenon’s Block
• Tenon’s capsule: this layer of connective tissue around the
globe, close opposition to the conjuctiva
• Sub-Tenon’s space: a potential space between the capsule
and the sclera. The instillation of LA into it produce analgesia
and akinesia by diffusing posteriorly into the retro-orbital
space to block the transversing sensory and motor nerves
• Duration of anaesthesia: > 1 hour
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Perceived as a safe alternative to
both the retrobulbar and peribulbar
blocks

15. Facial nerve block
• Various technique of facial nerve block have been described
Include:
- Van Lindt (most common applied)-only zygomatic branches of
facial nerve blocked
- O’Brien
- Atkinson
- Nadbath
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16. GENERAL ANAESTHESIA
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17. Intraocular pressure (IOP)
• normal IOP: 10-20 mmhg
• The blood supply to the retina and optic nerve depends on the intraocular
perfusion pressure.
• A rise in the IOP will impair the operating conditions and may cause an
expulsion of intraocular contents with permanent damage to the eye
• May also impairs the blood supply, leading to a loss of optic nerve function.
• IOP= K[(OPaq - OPpl) + CP]
K = coefficient of outflow;
OPaq = osm. pressure of aqueous,
OPpl = osmotic pressure of plasma,
CP = capillary pressure
• This perfusion pressure is defined as the difference between the MAP and the
intraocular pressure (IOP).
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18. • Two thirds of the aqueous fluid is actively secreted by the ciliary
body by a sodium-pump mechanism.
• One third comes from passive filtration through vessels on the iris.
• Aqueous fluid is produced at a rate of 2 µL/min.
• Aqueous flows over the lens and through the pupil to bathe the
inner corneal endothelium. It then enters the angle of the anterior
chamber to flow through the trabecular meshwork to the canal of
Schlemm.
• The canal of Schlemm is continuous with channels to the episcleral
veins.
• IOP is primarily regulated by the resistance at the trabecular
meshwork.
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19. • Impairment of aqueous drainage at any point can
elevate the IOP.
• Open-angle glaucoma  Sclerosis of the
trabecular meshwork is believed to cause the
chronic pressure elevation.
• Closed-angle glaucoma  obstruction to
aqueous drainage from closure of the anterior
chamber angle. E.g: peripheral iris swelling or
anterior displacement.
– Patients with a preexisting narrow angle may be
predisposed to this condition.
– The acute increase in pressure causes severe pain.
This is an ophthalmologic emergency.
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20. Factors affecting IOP
• Extrinsic compression of the eye also increases the IOP.
• A normal blink increases the IOP by 10 mm Hg.
• A forceful lid squeeze can increase IOP to more than 50 mm Hg.
• A poorly placed anesthesia mask can put enough pressure on the
eye to reduce blood flow to zero.
• Deep inhaled or thiopental anesthesia causes a dose-related
reduction in IOP by 30% to 40%.
• Opioids have little effect. Atropine in the usual doses does not
cause a significant increase in IOP, even in patients with open-
angle glaucoma. Ketamine may cause a modest increase in IOP.
• IV succinylcholine causes IOP to increase by 6 to 12 mm Hg. This
lasts for 5 to 10 minutes. The use of succinylcholine for induction
in cases of open-globe injury with full stomach has been
controversial. 20

21. Anaesthetic factors increasing
IOP
• External pressure of globe by
tightly applied FM
• Raised venous pressure-
coughing, straining, vomiting
• Raised arterial pressure
• Hypoxia and hypercarbia- cause
vasodilatation of intraocular
blood vessels
• Suxamethonium - the precise
mechanism is unknown but may
be due to contraction of
extraocular muscles during
fasiculation or dilation of blood
vessels.
• Ketamine
• Reduced venous pressure- head
up tilt.
• Lowered arterial pressure - at
systolic pressures <90 mmHg IOP
is proportional to the blood
pressure.
• Hypocarbia- constricting
choroidal vessels.
• Drug -Intravenous induction
agents (except ketamine).
Non-depolarising muscle
relaxants.
Acetazolamide- inhibits
production of aqueous
mannitol- reduction in
vitreous volume-
• Inhalational agents
21
Anaesthetic FactorsAnaesthetic Factors
reducing IOPreducing IOP

22. STEPS TO REDUCE IOP
 Adequate Premedication.
Heavy sedation with opiates is best avoided because of the dangers of
respiratory depression and hypercarbia.
 Induction. Thiopentone & non- depolarizing muscle relaxant
 Laryngoscopy.
 Should be performed until the patient is fully paralysed in order to avoid gagging or
coughing.
 IV lignocaine or esmolol to obtund sympathetic reflex
 Position. Head up tilt 15-20o
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23. Monitoring. ECG, oximeter, capnograph
Reversal-smooth emergence reversal
Extubation.
- Extubate early-to avoid coughing & bucking on the
ETT
- Anti-emetic may be administered to minimized the
incidence of post operative vomiting.
Post Operative Analgesia. Morphine 0.1 mg/kg if
required. No food or drink should be administered
for 3 hours to reduce the possibility of aspiration of
gastric contents.
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24. OCULOCARDIAC REFLEX
• Can occur in any age group during a variety of procedure
• Most common in paediatric-correction of strabismus
• Causes:
-ocular manipulation
-pinching of conjunctiva
-traction of extraocular muscle
-manual pressure on the globe
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25. Pathophysiology
• The reflex is mediated by reflex connected between
trigeminal nerve & vagus nerve
• The afferent tract derived mainly from ophthalmic division of
trigeminal nerve
• Synapse with motor nucleus of vagus nerve, located in
reticular formation of brainstem
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26. 26

27. • Management
- inform surgeon stop the stimulation
- ensure adequate ventilation-avoid hypoxia & hypercarbia
- increase depth of anaesthesia
- consider IV atropine
• The reflex may be seen more often with procedures under topical anesthesia. Retrobulbar
block is not uniformly effective, however, at preventing the reflex. Orbital injections can
trigger the response. The response is exacerbated by hypercapnia or hypoxemia.
• The ventilatory status is assessed. If significant bradycardia persists or recurs, intravenous
atropine is administered in 7 µg/kg increments.
• Rarely, severe bradycardia or asystole occurs.
• Usually the heart rhythm returns to normal with cessation of manipulation alone.
• The response fatigues with repeated stimulation.
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28. • Oculorespiratory reflex
– May cause shallow breathing, reduce respiratory
rate and even full respiratory arreast
– The afferent pathway are similar to the above
reflex and it is thought that a connection exist
between the trigeminal sensory nucleus and the
pneumotactic centre in the pons and medullary
respiratory centre.
• Oculoemetic reflex
– Is likely responsible for the high incidence of
vomiting after squit surgery (60-90%)
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29. Systemic effects of ophthalmic drugs
Drug MOA Side effects
timolol (use in
glaucoma)
long acting B-
adrenergic blocker
Bradycardia
palpitation
congestive cardiac
failure
Exacerbation of BA
PHENYLEPHRINE
(mydriatic)
Sympathomimetic drug Bradycardia
palpitation
hpt
nervousness
ATROPINE
(mydriatic)
anticholinergic tachycardic
flushing
agitation in elderly
central anticholinergic
syndrome
Acetazolamide
(carbonic anhydrase
inhibitor)
Reduce aqueous
production
alkaline diuresis
excretion of sodium &
potassium 29

30. Use of nitrous oxide
-interaction with Sulphur hexafluoride (SF6)
Sulphur hexafluoride (SF6)
• inert gas
• odourless, colourless, height molecular weight
• poorly water soluble
• poorly diffusible-retained in eye for long period
• exert tamponade effect
• total resorption 7-10 days
• remains as a single bubble, deepening the AC
until aqueous gradually replaces it.
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 SF6 tamponades the retina; dramatic rise in IOP as N2O
enters the gas space in the globe.
 When nitrous oxide is discontinued, IOP decrease to
lower then normal detrimental to retinal repair
 Cause retinal to re-detach when tamponading effect is
lost

31. Management
• Discontinue nitrous oxide at least 15 min prior
intravitreal gas injection
• Avoid nitrous oxide up to 10 days after SF6 injection
• Use TIVA technique
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 Silicone oil
-used in case where the tamponading effect is desirable
over a longer period of about 3 months before removed

32. Anticoagulation
• weigh the relative risks of thrombotic against
possible hemorrhagic complications.
• In a study of more than 19,000 cataract procedures,
the incidence of hemorrhagic and thrombotic
complications was very low.
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33. • A consensus is developing that cataract surgery may be safely
performed while maintaining patients on warfarin.??
• Usual practice is to stop the warfarin and aim INR < 1.8-2.0.
• For intermediate-risk procedures, such as some glaucoma
surgeries, stopping warfarin for 4 days preoperatively is
indicated.
• For high-risk cases for hemorrhage or thrombosis, conversion
from warfarin to heparin may be required.
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34. PENETRATING EYE INJURY
• Emergency surgery with possibility of full stomach
• Prevention of additional increase in IOP is the goal.
• Exclude other injuries-head, neck, chest, abdominal etc.
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Issues:
1.Elevation of IOP pre and
intraoperative
2.Risk of extrusion of vitreous
3.Hemorrhage
4.Lens prolapse

35. Management - Pre-op
1. Adequate fasting
2. May give metochlopramide  hasten the gastric
emptying & increase lower oesophageal sphinter
tone
3. Discuss with surgeon regarding prognosis of
affected eye
– Take step to avoid increase in IOP  if the eye is
salvageable
– Treat as ordinary emergency if eye is not
salvageable
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36. Induction & intubation
1. Rapid sequence induction
2. Avoid holding FM too tightly causes compression of eye globe
3. Aviod Scolene and Ketamine as possible
– precurarization with 1/10 the dose of non-depolarising muscle relaxant prior to scoline
(may reduce muscle fasciculation)
1. Induction with fentanyl 2mcg/kg and IV propofol 2mg/kg
2. Pressure response can be moderated by IV lignocaine 1mg/kg, IV esmolol 0.5mg/kg
3. If no airway problem anticipated, use modifies RSI with Rocuronium calculated dose 4 x ED
95 (1-1.2mg/kg) and wait for 60 secs.
4. Cricoid pressure is maintained throughout intubation to prevent aspiration
5. Gentle laryngoscopy by experienced anaesthetist
6. Standby Sugammadex (16mg/kg) if Rocuronium is used.
7. Propped-up head 15 degree to assist venous drainage
8. Avoid hypoxia, maintain normocarbia
9. Smooth emergence, aim for deep extubation if no risk of difficult airway and aspiration
10. Precaution for PONV: Dexa 5-10mg IV upon induction; Ondansetron 4-8mg IV and droperidol
0.625 – 1.25mg IV prior to extubation
Post op analgesia :
PCM and NSAIDs is preferred to avoid vomiting.
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37. Anesthesia-Related Eye Injuries
• Be aware of possible ocular damage during anesthesia
and surgery.
• If a patient emerges from a GA complaining of vision
impairment  emergency because of the possibility
of central retinal artery occlusion.
• A second potential complication is corneal abrasion.
– GA has been shown to decrease basal tear production.
Proper eye care with taping of lids with or without an
ocular lubricant provides protection.
– If a patient emerges from GA with eye pain or a foreign
body sensation, the patient must be followed up to ensure
improvement.
– If left untreated, corneal abrasions can progress to form
corneal ulcers.
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38. Points to Remember
• Take active measures to prevent surges of IOP at all times
• Close monitor of the ECG to detect and treat oculocardiac
reflex
• Ensure adequate neuromuscular blockade to avoid sudden
cough or movement, which may be disastrous in eye surgery
• Consider the use of anti-emetic to prevent PONV especially in
high risk patient
• Consider extubation in deep plane of anaesthesia to avoid
coughing and bucking on the ETT in suitable patients.
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39. References
• Manual of Anaesthesia, CY Lee,
2006
• Miller’s Anaesthesia, 7th
Edition,
2010.
• Commonly Asked Questions, Final
M.Med (Anaesthesiology),
Mahamarowi Omar.
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