Lateral canthotomy

Orbital compartment anatomylateral canthotomy

Procedure that releases lateral canthal tendons to allow orbit to expand anteriorly.  Used when there’s an increase in orbital pressure.  The orbit is not very expandable so an increase in pressure that exceeds perfusion pressure causes ischemia of the optic nerve and retina.

Indications –> Increased orbital pressure resulting in acute loss of visual acuity, IOP greater than 40 mm Hg.

Contraindications –> Suspected globe rupture

S/Sx of suspected globe rupture –> Hyphema, irregularly shaped pupil, exposed uveal tissue

Causes –> Retrobulbar hematoma (most common indication), tumor, intraocular emphysema, inflammation/orbital cellulitis

Anatomy

The globe and the optic nerve/retrobulbar contents are encased by 7 bony structures.  There’s the frontal, zygomatic, palatine and “SMEL” bones.

Orbital compartment bones

The nasal/medial aspect of the orbital compartment is made up of the bones whose acronym is SMEL:

Sphenoid

Maxillary

Ethmoid

Lacrimal

Procedure

Anesthetize the lateral canthus w/ lidocaine + epi or xylocaine + epi.  Inject towards the lateral orbital rim, starting once you’ve hit the orbital bone.

Use straight hemostat to crimp the lateral corner of the pt’s eye (advance hemostat all the way to orbital rim) for 1-2 minutes.  Will control hemostasis and form skin indentation to mark incision line.

Remove hemostat and incise the skin w/ scissors lateral to the eye 1-2 cm outwards/laterally.

Continue to cantholysis by retracting first the lower lid to expose and incise the inferior crus of the lateral canthus.  If IOP remains > 40 mm Hg, continue on to incise the superior crus of the lateral canthus.

Check visual acuity, pupillary response and IOP.  Call ophthalmology to arrange follow up.

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