DECIDETense proptotic eye + RAPD, acuity <6/18, IOP ≥40, or ophthalmoplegia → cut now. · Only contraindication: suspected globe rupture.
STEPS · ◆ KEY STEP — LOGGED WITH ITS TIME
TECHNIQUE — STEP BY STEP
Prepare: analgesia/sedation as needed; topical anesthetic drops; irrigate the area with saline.
Infiltrate lidocaine with epinephrine at the lateral canthus, needle away from the globe.
Crush: clamp the lateral canthus horizontally out to the rim for ~1 minute to devascularize the incision line.
Canthotomy: 1–2 cm horizontal cut from the lateral canthal angle to the rim.◆ LATERAL CANTHOTOMY CUT
Cantholysis: pull the lower lid up and out, strum the inferior crus, cut toward the earlobe.◆ INFERIOR CRUS RELEASED
Endpoint: the lid swings free and everts easily, fat is visible, the globe softens.
If the orbit is still tight, re-explore and finish the inferior release in stages.
After: no eye pad. Ointment, serial pupil and IOP checks, CT, ophthalmology.
EQUIPMENT
IN THE KIT — 6 ITEMS, ZIP-LOCK
3 mL syringe — for the lidocaine.
Needle to draw (blunt or 18 g).
Needle to inject (25–27 g).
Mosquito clamp — the 1-minute crush.
Toothed forceps.
Blunt-tipped iris scissors.
ALSO NEEDED — NOT IN THE KIT
Lidocaine with epinephrine — not in the kit; from the medication drawer.
Sterile saline for irrigation — never chlorhexidine or alcohol near the eye.
Topical anesthetic drops.
Tonometer (iCare/Tono-Pen) if available — trigger and endpoint checks.
Aftercare: antibiotic ointment (e.g. chloramphenicol); a clean polystyrene cup trimmed as a transport cover.
FIGURE
The cantholysis — cutting the inferior crus of the canthal tendon — is the step that decompresses the orbit; the canthotomy alone is just the exposure.
TRIGGERS: IOP ≥40 MMHG · VA <6/18 · RAPD
WINDOW: 60–90 MIN CRITICAL ISCHEMIA (SOME CITE 90–120)
CLAMP ~1 MIN · INCISION 1–2 CM · CUT THE INFERIOR CRUS
PITFALLS & PEARLS
Cutting skin only.
Iatrogenic globe injury.
If IOP is still high, the inferior tendon may not be fully cut. Re-explore.
Padding the eye, or delaying for CT or ophthalmology.