No matter what time of the day it is, this is an ophthalmic emergency and requires urgent management to save vision!

Orbital compartment syndrome occurs as a result of a raised intra-orbital pressure which can lead to permanent vision loss in as little as an hour if left untreated. (1)

What is it?

Orbital compartment syndrome is when the pressure within the orbit (intra-orbital pressure) is acutely raised typically following trauma. When the pressure exceeds that of the vascular perfusion of the ocular structures, ischaemia occurs and can result in vision loss. The management of orbital compartment syndrome is a sight-saving procedure.

What causes it?

Trauma to the face and/or the orbit is the most common cause. Haemorrhage behind the eye (retrobulbar haemorrhage) or oedema, leads to increased intra-orbital pressure (see the pathophysiology section below).

Pathophysiology

The orbit is an enclosed space and has limited space for expansion. The globe itself alongside the extraocular tissue fills approximately 26.5ml of a total 30ml volume, leaving little space for blood/swelling to fill in the event of injury (1).

The orbit houses the central retinal artery which branches from the ophthalmic artery of which the main supply is the internal carotid artery. 

When the pressure within the orbit exceeds that of these arteries, the structures allowing us to see including the retina and optic nerve will lose their blood supply causing ischaemia which can lead to complete and permanent vision loss. This typically occurs due to central retinal artery ischaemia, ischaemic optic neuropathy, or direct trauma to orbital structures.

How is Orbital Compartment Syndrome diagnosed?

It is a clinical diagnosis and therefore it is vital to get an urgent ophthalmological opinion. A delay in diagnosis and management can be sight-threatening.

Symptoms:

• Acute vision loss
• Ocular/ orbital pain 
• Diplopia

Whilst these symptoms overlap with many other ophthalmological conditions, it is very important to rule out orbital compartment syndrome as a priority.

Signs:

• Resistance to retropulsion – pushing gently on the globe through the upper eyelid will provide resistance relative to the other eye.
• Proptosis
• A tight orbit – tense eyelids
• Relative afferent pupillary defect (RAPD)
• Fixed, dilated pupil
• Reduced motility of the affected eye
• Raised intraocular pressure (IOP >40 with a suspicion of orbital compartment syndrome demonstrates the need for an urgent lateral canthotomy)
• Reduced visual acuity
• Colour vision reduction/red desaturation – would indicate optic nerve dysfunction

There may also be periorbital crepitus which would be indicative of emphysema from trauma.

On a dilated eye examination you may see:

• Optic disc oedema
• Central retinal artery occlusion
• Pulsation at the central retinal artery (2)

Patients should also get a CT of their orbits in order to assess the anatomy, however, management should not wait for these scans. If orbital compartment syndrome is confirmed clinically, patients should be managed first and then scanned to confirm the diagnosis.

Management

Discuss the patient with ophthalmology and it is very important to ask for senior input early (especially out of hours as an ophthalmologist may not be on site) as A&E registrars/ consultants are trained to perform the below procedure.

Gold standard: Lateral canthotomy and inferior cantholysis (LCIC)

This surgical procedure involves exposing and cutting the lateral canthal tendon which will allow complete mobilisation of the lower lid reducing intra-orbital pressure within minutes, relieving the pressure on the ophthalmic artery and optic nerve.

If this fails, urgent referral to an orbital surgeon will be required for orbital bone decompression. (1)

Often osmotic agents, carbonic anhydrase inhibitors and other pressure lowering medications can be used in order to reduce intra-ocular pressure.

Additional advice:

• Patients should not cough, strain or blow their nose as these can increase intra-orbital pressure acutely.

The important takeaway from this is that if you suspect orbital compartment syndrome, act fast!

References

1. Orbital compartment syndrome (2022) EyeWiki. Available at: https://eyewiki.org/Orbital_Compartment_Syndrome (Accessed: December 19, 2022). 
2. Turgut, B., Karanfil, F.C. and Turgut, F.A. (2019) Orbital compartment syndrome, Beyoglu eye journal. U.S. National Library of Medicine. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8842040/#:~:text=Orbital%20compartment%20syndrome%20(OCS)%20is,are%20vital%20to%20preserve%20vision. (Accessed: December 19, 2022). 

Written by Dr Matthew Mo (FY2) & reviewed by Edward Pritchard (ST7 Ophthalmology)