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

Features usually include:

• acute visual impairment
• periorbital bruising
• fixed, dilated pupil in the affected eye
• proptosis
• raised intra-ocular pressure
• the presence of an 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 unable to deal with large increases in intraorbital pressure.

Causes of increased intraorbital pressure include:

• retrobulbar haemorrhage (most commonly from trauma)
• infection
• emphysema (tension pneumo-orbitus)
• post surgical

Increased intraorbital pressure can quickly lead compression of the optic nerve and central retinal artery leading to ischaemia of the optic nerve and retina.

Radiographic features

CT

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

• proptosis
• tenting of the globe
• stretching of the optic nerve
• associated orbital fractures, intracranial haemorrhage 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.