Lateral Canthotomy & Cantholysis

Recognition

• History of orbital/periorbital trauma (or, rarely, spontaneous retrobulbar bleed on anticoagulation) with a tense, proptosed eye.
• Severe eye pain disproportionate to the visible injury.
• Relative afferent pupillary defect (RAPD) and progressively falling visual acuity.
• Ophthalmoplegia — reduced eye movements from a tight orbit.
• Tense, resistant globe on gentle palpation; measured intraocular pressure above ~40 mmHg supports the diagnosis, though this is a clinical emergency and treatment should not wait for a tonometry reading if the clinical picture is clear.

Why time matters

• Rising intraorbital pressure compresses the central retinal artery and optic nerve, causing progressive ischaemia.
• Retinal and optic-nerve ischaemia becomes irreversible within roughly 90–120 minutes of onset in the literature — some case series report better outcomes the earlier decompression occurs, with meaningful risk of permanent visual loss developing within the first two hours.
• Every additional minute without decompression increases the risk of permanent blindness — this is one of the few truly time-critical procedures a non-ophthalmologist may need to perform.

Preparation

• Explain the emergency nature of the procedure and obtain verbal/best-interests consent — this is not a procedure to defer for written consent.
• Infiltrate local anaesthetic with adrenaline at the lateral canthus to reduce bleeding and provide anaesthesia.
• Alert ophthalmology immediately — they should be involved as soon as possible, ideally before or concurrent with the procedure if time allows, but do not wait for them to arrive before decompressing.

Equipment

Step-by-step technique

1. Anaesthetise the lateral canthus

   Infiltrate local anaesthetic with adrenaline directly at the lateral canthal angle.

   LAST rescue — AAGBI algorithm ↗

2. Crush the lateral canthus

   Apply a straight clamp across the full thickness of the lateral canthal skin for 1–2 minutes — this crushes tissue to reduce bleeding when it is cut.

3. Cut the lateral canthus (canthotomy)

   Using straight scissors, cut horizontally through the crushed lateral canthus for 1–2 cm, dividing skin and the canthal angle down to the orbital rim.

4. Identify and release the inferior crus (cantholysis)

   Grasp the lower lid with forceps and pull it away from the globe. Identify the inferior crus of the lateral canthal tendon running from the canthus to the orbital rim. Insert scissors and "strum" the tendon with the scissor tip — you should feel a tight band; cut it, aiming inferoposteriorly (down and back, hugging the orbital rim) to avoid the globe.

5. Reassess

   Re-check intraocular pressure, visual acuity and proptosis. Improvement confirms adequate release.

6. Release the superior crus if needed

   If pressure remains elevated or the eye remains tense after inferior cantholysis, the superior crus of the tendon can also be divided in the same manner.

Lateral canthus & inferior crus

Aftercare

• Urgent ophthalmology review as soon as possible — this procedure buys time, it does not replace definitive care.
• Recheck intraocular pressure and visual acuity at intervals after the procedure.
• Arrange CT orbits once the eye is decompressed and the patient is stable, to define the underlying cause and extent of injury.
• Document indication, IOP before/after, visual acuity before/after, and which crura were released.

Complications

• Bleeding from the canthal incision — usually controlled with pressure; the crush step minimises this.
• Globe injury if scissors are directed toward rather than away from the eye — always aim inferoposteriorly, hugging the bony rim.
• Lacrimal system injury, particularly if the incision extends too medially.
• Ectropion or lid malposition on healing — a cosmetic complication, but sight always takes priority over cosmesis in this emergency.

References