Orbital compartment syndrome

Orbital compartment syndrome is an ophthalmological emergency referring to an increased intraorbital pressure that may lead to permanent visual impairment if left untreated.

Clinical presentation

Findings on exam may include:

• decreased visual acuity ⁶
• globe palpably tense and resistant to manual compression
• restricted lid motion
• proptosis
• raised intra-ocular pressure
• presence of a relative afferent pupillary defect
• restricted extra-ocular muscle movement

The condition is often seen in the context of trauma so other signs of trauma, particularly craniofacial, are usually present as well.

Pathology

The orbit is a conical space formed by the rigid bony orbit as the apex and the eyelid and orbital septum as the base. The eyelid and septum however are also relatively rigid and movement of the eyelids is also restricted by the medial and lateral canthal ligaments. The orbital compartment is therefore susceptible to an acute increase in pressure with an acute increase in volume. Potential etiologies of an acute increase in orbital compartment pressure include:

• retrobulbar hemorrhage
  • blunt trauma (most common cause)
  • retrobulbar or peribulbar injections
  • metastases
• infection
• emphysema (tension pneumo-orbitus)
• post surgical
• contrast extravasation

When the increase in orbital compartment pressure sufficiently diminishes the perfusion to the retina and optic nerve (via the central retinal artery and vasa nervorum, respectively) ischemia and vision loss may occur.

Radiographic features

CT

Although the diagnosis of orbital compartment syndrome is a clinical one, CT may show:

• proptosis
• stretching of the optic nerve
• tenting of the globe
  • may be defined by the presence of a posterior globe angle of less than 130 degrees
    • obtained by calculating the angle between medial and lateral tangential lines at the margin of the posterior globe which converge at the insertion of the optic nerve ⁶
  • the guitar pick sign refers to the resultant abnormally conical contour of the posterior globe 
• asymmetry/narrowing of the stretch angle
  • degree of discrepancy from contralateral eye may be correlated with diminished visual acuity ⁴
• retrobulbar hemorrhage
• associated orbital fractures, intracranial hemorrhage and other signs of trauma

Treatment and prognosis

Urgent decompression by performing a lateral canthotomy and cantholysis is required. Permanent visual damage can occur within one hour if the condition is left untreated.