Lateral Canthotomy: A Clinician’s Guide to the Sight-Saving Eye Procedure

What Is a Lateral Canthotomy?

A lateral canthotomy is an emergency procedure that cuts the outer corner of the eyelid to relieve dangerous pressure building up behind the eye. It buys time and blood flow when a patient’s vision is on the line.

In practice, it is almost always paired with a cantholysis, which releases the lateral canthal tendon that anchors the eyelid to the bony orbital rim. That tendon release is what actually decompresses the orbit.

This is a sight-saving procedure that belongs in the emergency clinician’s hands. Trained emergency physicians and advanced practice providers can perform it at the bedside, just as ophthalmologists do.

Lateral canthotomy is a classic high-acuity, low-occurrence (HALO) procedure. The stakes are high, yet you may go a year or more between cases, which makes it easy to get rusty.

When Is a Lateral Canthotomy Needed?

The procedure treats orbital compartment syndrome, most often caused by a retrobulbar hemorrhage after facial trauma. Blood collects behind the eye in a space that cannot expand.

Because the orbit is a closed bony box, that trapped blood raises pressure quickly. The rising pressure chokes the blood supply to the optic nerve and retina, so vision is at risk.

Recognizing the emergency early is half the battle. Keep OCS on your list for any patient with orbital trauma and sudden eye symptoms. You will act sooner and give the eye a better chance.

Orbital Compartment Syndrome

Orbital compartment syndrome (OCS) is rising pressure inside the bony orbit that outpaces blood flow to the eye. According to StatPearls, the orbit holds about 30 mL of volume and the globe fills roughly 7 mL of it, so there is little room to absorb bleeding.

When pressure climbs, perfusion to the retina and optic nerve drops. EyeWiki, from the American Academy of Ophthalmology, points to a rhesus monkey study on this. The retina may suffer irreparable damage with disrupted perfusion for as little as 75 minutes.

That figure, from an animal model in EyeWiki’s references, may not match human tolerance. Even so, it shows how fast the clock runs.

Retrobulbar Hemorrhage and Other Causes

Retrobulbar hemorrhage is the classic cause and the scenario where canthotomy is the fix. It usually follows blunt or penetrating facial trauma.

It can also follow orbital surgery or blepharoplasty, along with procedures such as a retrobulbar injection. In each case, bleeding into the orbit is what drives the pressure and threatens the eye.

Key Signs and the IOP Threshold

Watch for proptosis (a bulging, “rock-hard” eye), sudden loss of visual acuity, an afferent pupillary defect, and severe pain. Any of these signs can justify acting on their own.

Intraocular pressure (IOP) supports the picture. According to StatPearls, intraocular pressure measurements of 40 mmHg or higher indicate a soft threshold for intervention.

Key point: Treat “>40 mmHg” as a soft threshold that supports action, and let clinical signs stand on their own. If the signs point to OCS, do not wait for tonometry or a specific number before you cut.

Why Timing Matters

Speed protects vision, so the goal is to relieve pressure fast. StatPearls reports that elevated intraocular pressure lasting 60 to 100 minutes can cause permanent vision loss.

StatPearls teaches that best outcomes come from treating within about two hours of injury. That guidance should push you to move quickly.

The “two-hour rule” is a target that should prompt fast action while still leaving room for later treatment. Once you suspect OCS, the fastest safe decompression you can manage is the right call.

Time already elapsed is still a reason to act, not to hold back. Bailey and colleagues showed this at the University of Texas, in Ophthalmic Plastic and Reconstructive Surgery. Over half of participants with intervention more than 90 minutes after injury still showed visual acuity improvement.

If OCS is present, treat regardless of how long it has been. Later care can still return useful vision, so the procedure stays on the table well past the two-hour mark.

How a Lateral Canthotomy and Cantholysis Is Performed

This is a quick bedside procedure, and the steps are simple once you have done them a few times. First you anesthetize the area and crush the canthus for hemostasis. Then you make the skin cut and release the tendon.

Patients often ask if it hurts. You inject a local anesthetic first, and the relief from decompression usually matters far more to the patient than the small incision.

Position the patient supine and get good lighting before you begin. Have suction and gauze within reach, since a decompressed orbit can bleed briskly once the tendon is released.

Equipment You Need

Set up a small tray before you start. Everything below fits in a standard suture or laceration kit.

Item	Purpose
Local anesthetic with epinephrine	Numbs the area and limits bleeding
Iris or straight scissors	Cuts the canthus and the tendon
Toothed forceps	Grasps and stabilizes the lid margin
Hemostat	Crushes the canthus for hemostasis
Gauze	Controls bleeding and clears the field

Step 1: The Canthotomy

Inject local anesthetic with epinephrine into the lateral canthus. Then clamp the lateral canthus with a hemostat for about one minute to reduce bleeding before you cut.

Now make the skin incision. Per the Merck Manual, use iris scissors to cut from the lateral canthus to the orbital rim, approximately 1 to 2 cm.

Step 2: The Cantholysis

Grasp the lower lid with toothed forceps and pull it outward, away from the face. Point the scissors toward the patient’s nose and cut the inferior crus of the lateral canthal tendon. Many clinicians “strum” the tissue with the scissor tips to feel the tight band before cutting.

The cantholysis relieves the pressure, while the skin cut alone leaves the orbit tight. Skipping or under-doing the tendon release is a common trainee error. If pressure stays high, release the superior crus as well.

Aftercare

Leave the wound open to heal by itself and apply antibiotic ointment. Protect the cornea and keep it moist while the lids are lax.

Recheck IOP and visual acuity after the release to confirm the pressure dropped. Get ophthalmology or your specialist involved, but never let that call delay the procedure.

If pressure and symptoms have not eased, reassess your tendon release before anything else. Incomplete cantholysis is the usual reason a canthotomy fails to decompress the orbit.

How Effective Is It?

The numbers back up the effort. One 18-year retrospective series in The American Journal of Emergency Medicine tracked 60 patients at a single trauma center. There, lateral canthotomy lowered IOP by more than half, from a median of 50.0 mmHg before the procedure to 23.0 mmHg after.

Vision outcomes were strong too. In that same American Journal of Emergency Medicine series, over two-thirds of patients (43 of 60, 71.7%) were discharged with baseline vision. It was a single-center study, but the effect on pressure and sight is clear.

Contraindications and Risks

The main absolute contraindication is a suspected globe rupture. Cutting near a ruptured globe can worsen the injury, and rupture can mimic OCS, so examine carefully before you commit.

Beyond that, complications are uncommon and minor next to the benefit. Bleeding and mild lid deformity are possible, as is injury to nearby structures, but a threatened eye is the far bigger risk.

Anticoagulation and bleeding disorders raise the bleeding risk, yet they rarely change the decision when sight is on the line. When OCS is decompressing an eye, the benefit of acting usually outweighs these concerns. Weigh them, then proceed.

Staying Ready for a Procedure You Rarely Perform

Here is the honest problem. A clinician may perform a lateral canthotomy only a handful of times across a whole career, if at all. A skill you use that rarely fades between cases.

It is the kind of procedure many clinicians would hesitate to attempt without recent, hands-on practice. Knowing the steps on paper is a long way from your hands knowing them under pressure. The fix is to keep the motions fresh before you ever need them.

That gap is where deliberate rehearsal helps most. SimKit’s approach uses spaced repetition and deliberate practice to support ongoing review of rare procedures. Working through the motions on portable simulation models is meant to rehearse the steps before a real patient arrives.

Lateral canthotomy is one of the four Year 1 procedures in SimKit’s 12-month procedural training course. The kit ships a physical canthotomy model to your door, and the curriculum revisits it about every three months in roughly 30 minutes a month. That kind of hands-on procedural practice is designed to make a once-a-year skill feel familiar.

Frequently Asked Questions

What are the indications for a lateral canthotomy?

The main indication is orbital compartment syndrome with vision-threatening signs, usually from a retrobulbar hemorrhage. Act on the clinical signs or an IOP at or above the 40 mmHg soft threshold.

What is orbital compartment syndrome?

Orbital compartment syndrome is rising pressure inside the closed bony orbit that outpaces blood flow. That pressure starves the optic nerve and retina and can cause rapid vision loss.

Is a lateral canthotomy used for a retrobulbar hematoma?

Yes. A retrobulbar hematoma that raises orbital pressure and threatens vision is the classic reason to perform a lateral canthotomy and cantholysis.

Is a lateral canthotomy painful?

You give a local anesthetic first, and the discomfort is minor compared with the emergency and the relief that decompression provides.

Want to keep sharp on this and other rare emergencies? Tune in to the SimKit emergency medicine podcast for more procedural refreshers.