Canthotomy

What is Canthotomy?

It’s a Medical surgery procedure done by an ophthalmologist surgeon who is specialised in oculoplastic, an operation for lengthening the palpebral fissure by an incision through the lateral canthus also for restoration of the canthus.

Indications:

• Orbital compartment syndrome (OCS), an ophthalmologic emergency, which manifests with rapid, progressive vision loss, increased intraocular pressure, decreased extraocular motility, and pain in a patient with recent eye/orbital trauma or surgery

Blunt facial trauma (see Eye Contusions and Lacerations) may cause retrobulbar hematoma or severe oedema surrounding the eyeball, either of which can increase intraorbital pressure. Because the eye is constrained by the lids and the orbit, increased intraorbital pressure can cause intraocular pressure to rise rapidly and compress the optic nerve and its vascular supply. Untreated, this increased pressure causes permanent vision loss (OCS). Lateral canthotomy and cantholysis are done immediately to relieve intraorbital pressure and preserve vision if signs indicate OCS.

Contraindications:

Absolute contraindications

• Suspected globe rupture (eg, irregular pupil, hyphema, herniated iris tissue, shallow cornea, leak of aqueous humor)

Complications:

Complications may include

• Mechanical damage of the eye (eg, to the lateral rectus muscle, lacrimal gland, or lacrimal artery) or lids
• Haemorrhage
• Infection

The urgency of the procedure, combined with traumatic distortion of the anatomy and possible unfamiliarity with the procedure by non-ophthalmologists, may increase the risk of iatrogenic injury to the eyeball.

Equipments & Considerations required for the procedure:

• Sterile gauze, gloves, and drapes
• Antiseptic solution (eg, chlorhexidine, povidone-iodine)
• Topical ocular anaesthetic (eg, 0.5% proparacaine or tetracaine eye drops)
• Local anaesthetic (eg, 1% or 2% lidocaine with epinephrine), small injection needles, and small (about 3 mL) syringe
• Ophthalmic antibiotic ointment (eg, erythromycin5%, bacitracin)
• Sometimes, normal saline or water for irrigation
• Needle holder or hemostat, toothed forceps, iris scissors

Additional Considerations

• Speed of diagnosis of OCS and of execution of the canthotomy or cantholysis procedure is important to minimize the duration of retinal ischemia. Ophthalmologic consultation should be requested but should not delay the procedure. Because the diagnosis of OCS is purely clinical, the procedure also should not be delayed for imaging studies.
• Sterile technique is necessary.
• This procedure is painful. A conscious, confused, or uncooperative patient may require regional nerve block, sedation, or restraint to prevent movement that could result in damage to the eyeball during the procedure. Children may require general anaesthesia in the operating room.

Positioning

• Position the patient supine on the stretcher and stabilize the patient’s head and eyelids.

Relevant Anatomy

• The medial and lateral canthal ligaments contain the eye within the orbit and eyelids.
• The lateral canthal tendon has two branches: a superior and an inferior. Cutting one, or both loosens the eyelids and allows the globe to expand out of the orbit and thus relieve pressure on the eye.

Step-by-Step Description of Procedure:

• All preliminary steps should be done as quickly as possible, including rough estimation of visual acuity, an inspection of the globe, and sometimes a simple cleaning and irrigation of the lateral canthus area.
• Place all your instruments on a tray near the head of the bed, so everything is within easy reach and you don’t have to ask for assistance.
• Prepare the skin with an antiseptic agent such as povidone-iodine or chlorhexidine; do not allow the antiseptic to enter the eye. Drape the area.
• Inject 1 or 2 mL of a local anaesthetic containing epinephrine into the lateral canthal incision site.
• Use a needle driver or hemostat to crush the tissue from the lateral canthus to the rim of the orbit, for about 20 sec to 2 min. Crushing this tissue helps minimize bleeding and makes it easier to see where to cut when there is extensive traumatic oedema.
• Use iris scissors to cut from the lateral canthus to the rim of the orbit, about 1 to 2 cm (canthotomy).
• Cut the inferior and sometimes both crus of the lateral canthal ligament (cantholysis). Most experts recommend starting with the inferior crus. Lift the inferior portion of the lateral eyelid. With the scissors pointing away from the globe, identify and cut the inferior crus. “Strumming” with the scissors may help identify the inferior crus. If the tendon is still intact, you will feel a twanging like a plucked string.
• Next, some experts recommend routinely cutting the superior crus. Others recommend reassessing for relief of OCS (eg, by measuring intraocular pressure) and cutting the superior crus only if OCS persists.
• To cut the superior crus, lift and expose the underside of the lateral upper eyelid. Check whether the superior crus tendon has been cut by strumming across it with the scissors.
• If the tendon is still intact, cut it. Cutting the tendon loosens the eyelid and relieves pressure on the eye even more.

Aftercare

• Because the patient can’t blink to lubricate the cornea, apply an antibiotic ointment to the eye and cover it with a sterile dressing.
• Lateral canthotomy incisions are not sutured at the time of the canthotomy and often heal without significant scarring.
• Patients with severe injuries should be hospitalized.
• Methylprednisolone(ie, 250 mg IM/IV q 6 h) for 3 days should be considered for inpatients with progressive vision loss.
• If intraocular pressure remains elevated, topical therapy (eg, timolol5%, brimonidine0.2%, or dorzolamide 2% eye drops) or systemic therapy (eg, acetazolamide immediate-release 500 mg PO, or mannitol 1-2 mg/kg IV over 45 min) should be considered.
• Patients should avoid straining and apply ice packs for several days following canthotomy.

Note:

Warnings and Common Errors

• If a ruptured globe is suspected, avoid checking intraocular pressure or palpating the globe.

Tips and Tricks

• When cutting the inferior crus, aim anteroposteriorly toward the lateral rim to avoid injuring the levator muscle, lacrimal gland, and lacrimal artery, which are located superiorly.

NEXT STEP

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• The name of the test or procedure
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• What would happen if you did not have the test or procedure
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