Acute Orbital Compartment Syndrome

Updated: Jun 06, 2019
Author: Bryant C Shannon, MD; Chief Editor: Gregory Sugalski, MD 



Acute orbital compartment syndrome (AOCS) is a rare but treatable complication of increased pressure within the confined orbital space. It typically results from facial trauma or a surgical procedure, but many medical conditions have been known to cause AOCS (see Etiology). AOCS must be promptly diagnosed. If left untreated, patients with AOCS may develop retinal ischemia and subsequent irreversible blindness (see Treatment).[1]


The globe and retrobulbar contents are encased in a continuous cone-shaped fascial envelope that is nearly completely bound on all sides by the rigid, bony skull. Fibrous bands known as the tarsal plates form the anterior border, limiting movement. More superficially, the eyelids come together to form the palpebral fissure, which allows the eye to open and close. The lateral and medial aspect of the fissure is formed by the canthi, where the eyelids meet. The volume of an average adult orbit is 30 mL.[1]


The variable pathophysiology of acute orbital compartment syndrome has not been fully elucidated. The orbit may compensate for small increases in orbital volume by forward movement of the globe and prolapse of fat, but larger increases result in a rapid rise in orbital tissue pressures.

Therefore, although the orbit is not a fully enclosed space, it follows pressure-volume dynamics with a pathophysiology akin to other compartment syndromes, in which increased tissue pressures in an enclosed space lead to decreased perfusion. In cases of retrobulbar hematoma, the most common cause of AOCS, hemorrhage generally emanates from the infraorbital artery or one of its branches. In acute disease, retrobulbar blood can cause a substantial rise in pressure even with as little of 7 mL of blood.[2]

The optic nerve encases the central retinal artery anatomically, providing some protection. Other vessels within the eye are less protected, which often results in blindness without central artery occlusion in the case of anterior ischemic optic neuropathy.[3] Arterial blood flow has been demonstrated to cease at tissue pressures significantly lower than diastolic blood pressure.[2] Interestingly, why some patients with a retrobulbar hematoma develop orbital compartment syndrome while others do not is unknown. Retrospective analysis has not found fracture mechanism, degree of comminution, blood volume, or dislocation to be predictive of retrobulbar hematoma resulting in AOCS.[4]

This proposed mechanism associated with retrobulbar hematomas usually creates discernible and measurable physical signs of increased orbital pressure, which may prompt sight-saving emergency department therapy. Irreversible visual loss following trauma can also be caused by direct optic neuropathy from nerve impingement, crush, or transection or indirect traumatic optic neuropathy. The exact pathophysiology of indirect traumatic optic neuropathy has not been fully elucidated, but is thought to be a consequence of traumatic transfer of forces through the orbital bones to the intracanicular optic nerve axons and pial microvasculature, causing transient traction on these fragile structures.[5]


Retrobulbar hematoma is the most common cause of orbital compartment syndrome. Physical facial assault, motor vehicle collision (MVC), and falls are most frequently implicated in traumatic retrobulbar hematoma.[6] Additional traumatic etiologies include intraocular hematomas, orbital emphysema tracking from a sinus, and subperiosteal hematoma. In one case report, even extension of a subgaleal hematoma resulted in a delayed orbital compartment syndrome (OCS) in a patient with a known bleeding disorder.[7]

Atraumatic causes of AOCS are typically the result of facial surgery. However, AOCS has been reported in large-volume resuscitation, extravasation of contrast material, spontaneous bleeding in the setting of disseminated intravascular coagulation, mass lesions, sclerotherapy, and thyroid-associated orbitopathy.[8]

Risk factors

Patients on antiplatelet or anticoagulation therapy have been found to have a high rate of traumatic retrobulbar hematoma.[9] In addition, case reports have described patients with known bleeding disorders having delayed or atypical presentations. Conversely, orbital blowout fractures have been found to be protective against AOCS, as the "compartment" is disrupted by the displaced facial fracture.


Acute orbital compartment syndrome is considered a rare complication of facial trauma or surgery. A retrospective review of 727 patients with facial fractures found that 67% sustained some degree of ocular injury.[10] Of these injuries, 18% were categorized as serious and 3% as blinding. All of the latter resulted from optic nerve injury, retinal detachment, or corneal-scleral rupture. Other studies have found AOCS to occur in less than 0.1% of all cases of facial trauma[9] and in 3.6% of patients with diagnosed orbital trauma.[6]


Acute orbital compartment syndrome with visual acuity loss is associated with a poor prognosis. Permanent blindness occurs if effective therapy is not initiated promptly. AOCS due to retrobulbar hematoma is the most common cause of blindness associated with facial trauma.[4]

Emergent decompressive surgery may be sight-saving in patients with severe symptoms. Significant evidence shows that long-term outcomes correlate with time to intervention in patients with severe AOCS.[11] Half of patients presenting with decreased visual acuity due to retrobulbar hematoma experience immediate resolution of symptoms with emergent decompression. Irreversible visual loss can be expected with retinal ischemia that lasts longer than 120 minutes,[12] although some patients may experience partial recovery with decompression outside this window.[6]

Patient Education

For patient education information, see the Eye and Vision Center, as well as Black Eye.




Symptoms of acute orbital compartment syndrome may include the following:

  • Eye pain
  • Diplopia
  • Visual loss
  • Reduction of ocular motility
  • Proptosis

Physical Examination

Physical examination should not be delayed in patients with acute trauma, as progressive periorbital swelling can obscure the examination. Examination is typically conducted in an external to internal progression, as follows:[13]

  • Proptosis (best visualized in perpendicular plane with the patient in semi-reclining position)
  • Ecchymosis of eyelid
  • Chemosis
  • Tactile firmness/tense orbit (helpful in unconscious patients)
  • Intraocular pressure
  • Visual acuity
  • Ophthalmoplegia
  • Afferent pupillary defect
  • Red light reflex
  • Fluorescein stain (useful for Seidel sign if rupture is a concern)
  • Papilledema
  • Central retinal artery pulsation
  • Pale optic disc (late)
  • Cherry-red macula (rare)


Diagnostic Considerations

Problems to be considered in the differential diagnosis of orbital compartment syndrome include the following:

  • Direct optic neuropathy from nerve impingement, crush, or transaction
  • Graves orbitopathy
  • Orbital neoplasm
  • Direct injury from surgical dissection
  • Lens dislocation

Differential Diagnoses



Laboratory Studies

No laboratory studies are absolutely indicated in the workup of patients with acute orbital compartment syndrome (AOCS). Baseline routine laboratory evaluation may be requested for a patient who requires urgent medical treatment or urgent surgical decompression or to evaluate for use of anticoagulation therapy. 

Imaging Studies

CT scanning or MRI of the orbit may help to identify the etiology of compression and to exclude alternative diagnoses. The radiological sign often associated with AOCS is a posterior angle of the eye inferior to 130° (“globe tenting”), observed in 75% of cases.[11] Additionally, some evidence correlates severe findings with prognosis of visual loss.[14] While ultrasonography has not been validated for AOCS, studies have shown its diagnostic utility in evaluating for alternative traumatic ocular pathologies, including retinal detachment, central retinal artery occlusion (CRAO), lens dislocation, vitreous hemorrhage, and vitreous detachment.[15]

Other Tests

Once globe rupture has been excluded, IOP should be promptly measured. Normal IOP pressure ranges from 10-20 mm Hg, with an acceptable difference between each eye of 3-6 mm Hg.[13] Pressures greater than 40 mm Hg should be promptly treated (see Treatment). The examination is not static and should be repeated with any changes in pain or symptoms or periodically in high-risk patients.



Initial Management

Trauma evaluation should proceed as per standards for patients with head trauma/multiple trauma, with assessment for life-threatening injuries and stabilization for transport.

Treatment of pain, agitation, and emesis may be appropriate to avoid further increase in intraocular pressure (IOP). Protective eye shields should be used during transport upon concern for penetrating eye injury or scleral rupture. If intubation is necessary and not otherwise contraindicated, some evidence suggests using rocuronium over succinylcholine, as succinylcholine has been demonstrated to increased intraocular pressure, although clinical significance has never been studied.[16, 17]

Head imaging should be prioritized to evaluate for possible retrobulbar hematoma. If head imaging is delayed or if the history or physical examination reveals concerning features for AOCS, emergent surgical decompression should be immediately considered. Emergent indications include known retrobulbar hematoma with an afferent pupillary defect (APD), vision loss, or proptosis. Facial trauma with an IOP of more than 40 mm Hg is an additional indication. Less-sensitive signs include isolated APD, ophthalmoplegia, cherry-red macula, optic nerve head pallor, and severe eye pain. Patients not meeting criteria for emergent decompression should undergo medical management with hyperosmotic agents, steroids, and serial visual acuity examinations and IOP assessments.

Surgical Decompression

Possible AOCS with concerning features must prompt immediate decompression of the orbital pressure (< 2 hours from onset).

The emergency procedure of choice for acute loss of visual acuity associated with acute orbital compartment syndrome is dissection of the lateral canthus and disinsertion of at least the inferior crus of the lateral canthal tendon (ie, inferior cantholysis). This procedure allows complete mobility of the lower lid.  

In cadaver laboratories, lateral canthotomy/cantholysis and inferior orbital septum release are equally effective at reducing orbital compartment pressure. Additionally, the data support an additive synergistic reduction in compartment pressure when the procedures are both performed.[18, 19] However, the ease of the procedure and comfort of the provider should be considered when deciding which to perform. Most nonfacial surgeons should perform a lateral canthotomy and inferior cantholysis. It is technically less complex and can be performed in low–resource settings with just a scalpel and basic medical clamp.[20]

Lateral canthotomy alone does not relieve raised intraorbital pressure. The lateral canthal tendon firmly anchors the eyelids to the orbital rim. The subsequently performed cantholysis allows the orbital contents to expand forward, relieving intraorbital pressure. Commonly, inferior cantholysis is then performed, with consideration of an additional superior cantholysis if increased pressures persist.[21, 22]

Lateral canthotomy[1, 2, 23]

Steps of lateral canthotomy are as follows:

  1. Clean the area with sterile saline.
  2. Inject approximately 1 mL of lidocaine 1% into the lateral canthus.
  3. Apply a hemostat/clamp with one side anterior and one side posterior to the lateral canthus and advance approximately 1 cm until the rim of the bony orbit is felt.
  4. Clamp for 1 minute.
  5. Carefully cut through the crushed, demarcated line to the orbital rim/lateral fornix to avoid traumatizing the orbit.
Lateral canthotomy is performed by incising latera Lateral canthotomy is performed by incising laterally with sharp scissors.

Inferior cantholysis

The steps of inferior cantholysis are as follows:

  1. Grasp the lower eyelid with forceps and retract down and out from the orbit.
  2. Place the lateral side of an opened pair of curved scissors against the palpebral conjunctiva of the lateral eyelid.
  3. Sweep toward the lateral canthotomy incision.
  4. Identify and incise the inferior crus of the lateral canthal ligament.
  5. The ligament will impede lateral movement of the scissor blade. This technique is recommended in traumatic AOCS, as traumatic edema can complicate visual identification of the ligament.
  6. Verify laxity of the lateral canthus to confirm successful dissection.
  7. Recheck the IOP and visual acuity. Consider repeating the procedure to dissect the superior crus if IOP is not immediately improved.
Cantholysis is performed by identification and dis Cantholysis is performed by identification and disinsertion of the inferior crus of the lateral canthal tendon, which should allow free mobility of the lower lid margin.

In patients who require lateral canthotomy with inferior cantholysis, IOP normalizes, decreasing by an average of 35 mm Hg.[6] If visual acuity fails to improve, an ophthalmologist should be notified immediately for consideration of subperiosteal hematoma, operative orbital decompression, or hematoma evacuation. Reports have described patients requiring interventional neuroradiology for treatment of refractory AOCS because of ongoing bleed.[24] Physical examination findings such as proptosis and abnormal extraocular movement may not immediately improve and are less-reliable markers of successful decompression.

Conservative Management

Conservative or nonsurgical management of early AOCS is appropriate if the examination findings are reassuring and stable and frequent re-examinations are possible. The goal of pharmacotherapy is to reduce morbidity and to prevent complications. Several medications are used to decrease intraocular pressure (IOP) and reduce inflammation and oxidant effects, including steroids, hyperosmotic agents, and carbonic anhydrase inhibitors.[3] Other nonsurgical options for management are not supported by data but are centered on reducing intraorbital pressure via elevation of the head of the bed, calming the patient, and ice.[5]

Although the definitive management of AOCS is decompression, some data support routine use of hyperosmotic agents such as mannitol to decrease IOP if surgical decompression is delayed or in preparation for decompression. However, this benefit seems to be inconsequential if surgical decompression is performed in a timely manner.[25] In one study, intraocular pressures were reduced by over 25 mm Hg in patients who were first managed medically.[6]

Steroids in the treatment of AOCS are considered controversial. Initial recommendations were extrapolated from studies showing benefit in motor function in patients with spinal cord injury.[26] More recent data from the CRASH trial have shown increased mortality with administration of steroids in patients with head trauma. Animal models have shown that steroids increase axonal loss after optic nerve trauma.

In general, insufficient studies show medical management to be as effective as surgical management for AOCS. In patients in whom immediate surgical decompression is not indicated or in those in whom surgical decompression has been delayed, it is reasonable to trial conservative management in addition to repeat eye examinations (eg, acuity, IOP).[5, 27]


Emergent ophthalmologic consultation is required whenever an acute orbital compartment syndrome diagnosis is entertained. If necessary, transfer for specialty consultation and/or further workup (including CT scanning or MRI) is indicated once the patient is stabilized and after elevated IOP is treated.

Emergent oromaxillary facial surgery consultation is required if the etiology is postsurgical. In addition, an oral and maxillofacial surgeon (OMFS) should be consulted when hemorrhage is suspected within the optic canal or optic nerve sheath.


Among inexperienced providers who perform lateral canthotomy with cantholysis, the most common pitfall is incomplete canthal release. This is often a consequence of incompletely exposing the tendon during initial lateral dissection.

Most incisions heal on their own, while some require delayed closure (2-3 days).[26] Iatrogenic complications are rare and can be managed less emergently; they include infection, cosmetic deformity, and functional impairment.[2] If performed with instruments parallel to the surface of the globe with good retraction, injury to the globe or extraocular muscles is exceptionally uncommon.



Medication Summary

The goal of pharmacotherapy is to reduce morbidity and to prevent complications. Several medications are used to decrease intraocular pressure (IOP) and reduce inflammation and oxidant effects, including steroids, hyperosmotic agents, and carbonic anhydrase inhibitors.[3]

Hyperosmotic Agents

Class Summary

These agents decrease IOP by direct osmosis of water in the orbit.

Mannitol (Osmitrol, Aridol)

Mannitol is used for immediate pressure relief by osmotically shrinking the vitreous and dehydrating the intraorbital and intraocular spaces.

Carbonic Anhydrase Inhibitors

Class Summary

These agents decrease IOP by decreasing production of aqueous humor in anterior chamber. Additionally, they reduce systolic blood pressure, which may help control hemorrhage.

Acetazolamide (Diamox)

Acetazolamide inhibits the enzyme carbonic anhydrase, reducing rate of aqueous humor formation, decreasing IOP, but not acutely. This agent is used for adjunctive treatment of chronic simple (open-angle) glaucoma and secondary glaucoma and preoperatively in acute angle-closure glaucoma when delay of surgery is desired to lower IOP.


Class Summary

These agents exert an anti-inflammatory effect and an antioxidant effect that decreases production of free-radical metabolites.

Methylprednisolone (Solu-Medrol, A-Methapred, Depo-Medrol)

Methylprednisolone reverses increased capillary permeability.

Dexamethasone (Baycadron, Decadron, Dexamethasone Intensol)

Dexamethasone reduces inflammation and stabilizes the cell membrane against ischemic damage.


Class Summary

These agents decrease IOP by decreasing production of aqueous humor.

Timolol ophthalmic (Betimol, Timoptic, Istalol)

This agent may reduce elevated and normal IOP, with or without glaucoma, by reducing production of aqueous humor.

Local Anesthetics

Class Summary

Anesthetics that inhibit depolarization of type C sensory neurons are used for decompressive procedures.

Lidocaine (Akten)

Lidocaine is an amide local anesthetic used in a 1-2% concentration. It inhibits depolarization of type C sensory neurons by blocking sodium channels. Lidocaine is available in combination with epinephrine, which prolongs the anesthetic effect and enhances hemostasis (maximum epinephrine dose 4.5-7 mg/kg).