2.4 Post-Op Eye Pain Flashcards
HistoRY
A 66-year-old previously fit and well male patient had a total hip
replacement under a general anaesthetic. In recovery, he is complaining of
unilateral eye pain.
What is your differential diagnosis?
- Ocular causes
Conjunctivitis
Corneal abrasion
Corneal ulceration
Foreign body
Trauma
- Orbital causes
Glaucoma
Iritis
optic neuritis
Migraine
Trauma
What are the most common/
likely causes?
- Corneal abrasion due to mask, eye tape, and decreased tear production
- Chemical injury from antiseptic solutions and drugs
- External pressure resulting in optic neuropathy
- Retinal ischaemia
- Exacerbation of glaucoma
What are the factors that make a patient high risk to attaining an eye injury?
- Position
° Lateral: abrasion/trauma
° Prone: optic nerve pressure/conjunctival oedema
- Position
- Pre-existing eye disease
- History of diabetes and hypertension
- Prolonged surgery
What is glaucoma?
Glaucoma is the condition
where the free flow of aqueous humour is hindered,
which can increase the intraocular pressure (IOP).
- Closed angle
- Open angle
- Normal tension glaucoma
In all types of glaucoma the loss of vision is due to optic nerve damage.
What is open angle glaucoma?
Open-angle glaucoma
(chronic glaucoma)
is the condition in which aqueous fluid drains
very slowly due to clogging of the trabecular mesh.
What is Closed-angle glaucoma,
also called acute glaucoma,
is an ophthalmologic emergency.
This occurs when the
iris completely blocks fluid access to the trabecular meshwork.
The pressure builds up, causing the patient
excruciating eye pain, and vision is lost quickly.
What is Normal Tension Glaucoma
In normal tension glaucoma
optic nerve damage is present
but with normal IOP.
The cause is mainly familial and
history of systemic heart disease such
as irregular heart rhythm.
What are the determinants of IOP?
IOP is dependent on
- Contents, such as volume of aqueous, vitreous, and blood
- Scleral compliance
- Tone of extra ocular muscles
4 * Drainage of aqueous, which depends on venous pressure
What are the normal values?
Normal IoP = 16+/− 5 mmHg; >25 mmHg is pathological.
can the ioP be normal in glaucoma?
Yes.
In open-angle and normal tension types,
the IoP can be normal.
The sclera adapts to increased volume, and hence IoP is normal.
Explain the pathophysiology
of closed-angle glaucoma.
Normally the aqueous humour
produced by the ciliary body
is drained to the veins
through the Canal of Schlemm.
If the angle between iris and cornea is acute/blocked,
then the drainage is affected,
resulting in increased intraocular pressure.
- Pain and loss of sight in extreme conditions; “silent thief of sight”
Avoid drugs that dilate the pupils as this also can close the angle. See
Figure 2.6.
What is the effect of anaesthesia on ioP?
Consider IOP equivalent to ICP and structure your answers similarly.
Any increase in volume and pressure intraocularly
and obstruction to venous drainage
would cause an increase in IoP.
Drugs
Hypoxia, hypercarbia, neck ties/coughing:
increase IOP.
What is the effect of anaesthesia drugs on ioP?
- IV induction drugs:
decrease IOP except ketamine. - Muscle relaxants:
suxamethonium increases IOP up to 10 mmHg
due to extraocular muscle twitching.
This can be overcome by giving adequate dose of IV induction agents.
Non Depolarising muscle relaxants decrease IoP
How would you decrease the
ioP in an acute setting?
General
* Head up tilt
- Avoid neck ties/coughing/vomiting, etc.
- Maintain oxygenation, and avoid hypercarbia and hypotension.
Drugs
- Acetazolamide
- Mannitol
- Propofol
can you tell me the pathway of the light reflex?
Pupillary (light) reflex
II
Afferent—Optic nerve, which terminates in the pretectal area of midbrain.
Axons from here then radiate bilaterally
to terminate in the
Edinger-Westphal nucleus
→
Ciliary ganglion
→
parasympathetic postganglionic axons
travel in the short ciliary nerve
and end on the iris sphincter.
_______________________
Efferent - Oculomotor nerve
Ganglion—Ciliary ganglion
Central mediator—Occipital lobe of brain
