When and How to Perform a Lateral Canthotomy
A 35 yo woman presents to your rural emergency department. She has recently had eye surgery at a large tertiary centre and has been allowed home. Her presentation to the emergency department is:
- Increasing Headache
- Left Eye Pain
- There is proptosis of the eye
- Restricted Extra-Occular Eye Movements
- Decreased visual acuity
- Afferent Pupillary Defect
- Pressure in the affected eye of 40mmHg
This is an ophthalmological emergency. In perfect world, the treatment should occur first, however because we did not know what was happening a rapid CT was done, which demonstrated a retrobulbar haematoma, causing the proptosis and a stretching of the optic nerve.
Usually if the pressures are <30mmHg, medical management is acceptable, however when the pressures reach 40 mmHg, there is a need for immediate decompression by lateral canthotomy and cantholysis.
The procedure should be performed by an ophthalmologist, however when no-one is available, it becomes an emergency medicine procedure.
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.
Indications for Lateral Canthotomy:
- Retrobulbar Bleed
- Decreased Visual Acuity
- Afferent Pupillary Defect
- Increased Intra-occular Pressure- 40 mmHg and above of pressure requires decompression
Contraindications for Lateral Canthotomy:
A Potential Globe Rupture is the main contraindication. Findings that might point to that include:
- Irregular Shaped Pupil
- Subconjunctival Haemorrhage
- Conjunctival Tear
The procedure itself is relatively simple and is shown below in a video:
- Advise the patient and of what is to be done and get consent.
- Give gentle sedation. Our patient received 1mg IV midazolam, which was adequate
- Clean the area around the eye
- Inject 1-2ml of 1% lignocaine with adrenaline into the lateral canthus. Do not damage the globe
- Devascularise the Lateral Canthus: Use a small clamp to clamp the tissues for about 15-30 seconds.
- Make an Incision into the lateral canthus- staying away from the globe.
- Next cut the canthal tendons. These run superiorly and inferiorly and feel like guitar strings
There may be some bleeding, however this is easily controlled by direct pressure. The eye pressure should reduce almost immediately.
In our patient the eye pressure was measured within 5 minutes and had dropped to 29mmHg and then continued to drop further. The patient also had medical management including Diamox 250 qid and timolol eye drops.
Below is a video of the procedure: