The ability to perform a lateral canthotomy and cantholysis is an essential skill for every ophthalmologist and emergency room physician. It can be a vision-saving technique in the setting of decreased perfusion to the optic nerve or globe as a result of increased orbital pressure. In addition, it is a useful step in many common eyelid procedures. This tutorial will highlight the indications, materials, and technique used to perform a lateral canthotomy and cantholysis.

Indications

Orbital compartment syndrome

The orbit consists of four bony walls within the skull which angle posteriorly to form a cone:

• The roof is composed of the frontal and lesser wing of the sphenoid bone.
• The medial wall is composed of the ethmoid, lacrimal, maxillary, and sphenoid bones.
• The floor is composed of the maxillary, palatine and zygomatic bones.
• The lateral wall is composed of the zygomatic and greater wing of the sphenoid.
• The globe and the surrounding orbital rim mark the anterior border of the orbit.

The orbit is a closed compartment and therefore any expansile process within the orbit will cause increased pressure on the surrounding structures.

An example of this is a retrobulbar hemorrhage. Increased orbital pressure can cause the anterior displacement of the globe which manifests clinically as proptosis. The anterior displacement of the globe is limited by the eyelid complex which is anchored to the orbital rim primarily by the lateral and medial canthal tendons. In some cases, orbital pressure can increase above the perfusion pressure of the optic nerve leading to ischemia of the optic nerve and retina. This is a vision-threatening condition and should be addressed emergently.

Intraorbital pressure can be indirectly assessed by measuring intraocular pressure.

Clinical signs suspicious for decreased perfusion from orbital compartment syndrome include:

• decreased visual acuity,
• intraocular pressure higher than 35-40mmHg,
• a relative afferent pupillary defect or
• decreased arterial circulation of the optic nerve visualized by the absence of flow or pulsing of retinal arteries with minimal or no digital pressure on the globe.

Releasing the lateral canthal tendon from the orbital rim by performing a lateral canthotomy and cantholysis allows for more anterior displacement of the globe, leading to a reduction in intraorbital pressure and a return of optic nerve and retinal circulation.

Eyelid procedures

Many common non-emergent eyelid surgeries also require a lateral canthotomy and cantholysis.

The best example is the lateral tarsal strip. In this case the lateral canthal tendon is released and a new, shorter "lateral canthal tendon" is formed by anchoring the tarsus to the periosteum of the orbital rim. This effectively tightens the lower lid and can be an effective treatment for ectropion or entropion caused by increased lid laxity.

The lateral canthotomy and cantholysis can also be utilized in procedures which increase lower lid laxity in order to close full thickness lower lid defects.

Supplies

Most supplies are readily available for scheduled eyelid procedures. This is intended to be a checklist for supplies needed in the case of an emergent lateral canthotomy and cantholysis

• Topical proparacaine
• Local anesthetic (lidocaine 2% with epinephrine 1:100,000, syringe, 20 gauge needle to draw up anesthetic, 27 gauge needle to inject)
• Surgical drape
• Topical antiseptic (ex. Povidine-iodine)
• Surgical loupes
• Sterile gauze
• Utility, Stevens or Westcott scissors
• Iris scissors if available