aka Ophthalmology Befuddler 033
Examination of the right eye reveals:
- He is unable to detect light when the eyelids are passively opened.
- There is a relative afferent pupillary defect affecting the right eye.
- Extraocular movements are markedly reduced.
- Tonometry reveals an intraocular pressure of 45 mmHg.
Q1. What is shown and what is the likely diagnosis?
The right eye appears proptosed with a dilated pupil, extensive subconjunctival hemorrhage and bloody chemosis, as well evidence of periorbital swelling and hematoma.
The likely underlying diagnosis is:
Hemorrhage into the potential space within the rigid orbit and around the eye transmits pressure onto the optic nerve. Acute orbital compartment syndrome occurs when this results in a compressive optic neuropathy.
The main differentials are:
Q2. What are the clinical features of this condition on history?
- Symptoms — pain, decreased vision, inability to open the eyelids due to severe swelling.
- Cause —- history of trauma or surgery to the eye or orbit, or retrobulbar injection.
- Risk factors for spontaneous hemorrhage — bleeding disorder, anticoagulants and anti-platelet drugs, pregnancy.
Q3. What are the clinical features of this condition on examination?
- Visual acuity and visual fields — decreased with dyschromatopsia (signs of optic neuropathy)
- External exam — Proptosis with resistance to retropulsion, diffuse subconjunctival hemorrhage, tight eyelids (rock hard) with echymosis and chemosis.
- Extraocular eye movements — limited extraocular motility
- Pupils — RAPD.
- Tonometry — increased intraocular pressure (IOP)
- Funduscopy — papilloedema from compressive optic neuropathy may be present, retinal artery or vein occlusion.
Q4. What investigation should be performed and what are the typical findings?
CT orbit (axial and coronal views) can confirm the diagnosis — but if vision is threatened treat first!
Usual findings on CT:
- diffuse, increased reticular pattern of the intraconal orbital fat rather than a discrete hematoma.
- teardrop or tenting sign is ominous — it occurs when the optic nerve is at maximum stretch and distorts the back of the globe into a teardrop shape.
Q5. What is the treatment of this condition?
Therapy depends on whether there is compressive optic neuropathy or severely raised IOP:
- Evidence of optic neuropathy or severely raised IOP (>40 mmHg) —
lateral canthotomy and cantholysis should be performed immediately (ideally by an ophthalmologist); use procedural sedation in the ED if it does not cause a delay.
- No evidence of optic neuropathy but IOP is raised (e.g. >30 mmHg) —
treat with agents used to lower IOP (e.g. topical timolol, acetazolamide, mannitol; see acute glaucoma).
- Primary indications:
– Decreased visual acuity
– Intraocular pressure > 40 mm Hg
- Secondary indications:
– Afferent pupillary defect
– Cherry red macula
– Nerve head pallor
– Eye pain
– Globe rupture
Q6. how is a lateral canthotomy/ cantholysis performed?
The main steps in emergency canthotomy/ cantholysis are:
- use local anesthetic but warn the patient that they may feel pain
- Perform the canthotomy:
- place the scissors across the lateral canthus and incise the canthus full thickness
- Perform cantholysis:
- Grasp the lateral lower eyelid with toothed forceps
- Pull the lower eyelid anteriorly
- Point the scissors toward the patient’s nose, place the blades either side of the lateral canthal tendon, and cut.
Cantholysis is done more by feel than by visual identification of landmarks — the lower eyelid will come completely away from the globe once the tendon has been completely severed.
Videos showing a lateral canthotomy and cantholysis being performed:
- Ehlers JP, Shah CP, Fenton GL, and Hoskins EN. The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease (5th edition). Lippincott Williams & Wilkins, 2008.
- Johnson D, Schweitzer K, Sharma S. Ophthaproblem: Can you identify this condition? Retrobulbar hemorrhage. Can Fam Physician. 2009 Jun;55(6):605, 607. PMID: 19509203; PMCID: PMC2694083.
- Marx JA, Hockberger R, Walls RM. Rosen’s Emergency Medicine: Concepts and Clinical Practice, 7th edition (2009) Mosby, Inc. [mdconsult.com]
- McInnes G, Howes DW. Lateral canthotomy and cantholysis: a simple, vision-saving procedure. CJEM. 2002 Jan;4(1):49-52. PMID: 17637149. [fulltext]
- NSW Statewide Opthalmology Service. Eye Emergency Manual — An illustrated Guide, 2007. [link to free pdf]
- Pramanik, S. Assessment and Management of Ocular trauma. EyeRounds.org [fulltext]
- Perry M. Acute proptosis in trauma: retrobulbar hemorrhage or orbital compartment syndrome — does it really matter? J Oral Maxillofac Surg. 2008 Sep;66(9):1913-20. PMID: 18718400.