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Procedural Skills (SLO6)
Question 32 of 141
A 27 year old man presents to the Emergency Department after being hit in the right eye by a squash ball. His visual acuity is greatly reduced. You note proptosis and a resistance to retropulsion of the globe when pressure is applied through the eyelid. You are unable to invert the upper eyelid as it is taut against the globe. What is the most appropriate immediate management for this patient?
Answer:
Signs of a retrobulbar haemorrhage with orbital compartment syndrome (OCS) include decreased vision, elevated eye pressure, asymmetrical proptosis (eye bulge), resistance to retropulsion, and tight eyelids against the globe. A CT scan can reveal retrobulbar haemorrhage, but only a clinical exam will determine whether this bleeding is causing a compartment syndrome and requires treatment. Vision loss can occur after about 1.5 hours of impaired blood supply, so immediate treatment is imperative. Speed of diagnosis of OCS and of execution of the canthotomy or cantholysis procedure are important to minimise the duration of retinal ischaemia. 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.Lateral Canthotomy
Procedural Skills (SLO6)
Last Updated: 2nd March 2021
Lateral canthotomy, the emergency treatment for orbital compartment syndrome, is the surgical exposure of the lateral canthal tendon. Cantholysis is canthotomy plus incision of the inferior branch (crus) of the tendon. 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 intraorbital pressure on the eye.
Indications
- Orbital compartment syndrome (OCS)
- OCS is 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 may cause retrobulbar haematoma 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.
- Speed of diagnosis of OCS and of execution of the canthotomy or cantholysis procedure are important to minimise the duration of retinal ischaemia. 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.
Contraindications
- Suspected globe rupture
- (e.g. irregular pupil, hyphema, herniated iris tissue, shallow cornea, leak of aqueous humor)
Complications
- Mechanical damage of the eye (e.g. to the lateral rectus muscle, lacrimal gland, or lacrimal artery) or eyelids
- Haemorrhage
- Infection
Procedure
- N.B. This procedure is painful. A conscious, confused, or uncooperative patient may require regional nerve block, sedation, or restraint to prevent motion that could result in damage to the eyeball during the procedure. Children may require general anaesthesia in the operating room.
- Position the patient supine on the bed and stabilise the patient’s head and eyelids.
- 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 local anaesthetic containing epinephrine into the lateral canthal incision site.
- Use a needle driver or haemostat 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 minimise 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. When cutting the inferior crus, aim inferoposteriorly toward the lateral rim to avoid injuring the levator muscle, lacrimal gland, and lacrimal artery, which are located superiorly.
- Next, some experts recommend routinely cutting the superior crus. Others recommend reassessing for relief of OCS (e.g. 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 hospitalised.
- Methylprednisolone (i.e. 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 (e.g. timolol 0.5%, brimonidine 0.2%, or dorzolamide 2% eye drops) or systemic therapy (e.g. 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.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
