Orbital infection is a relatively commonly encountered pathology.
It comprises of three main clinical entities with the most important distinction between that of orbital and periorbital cellulitis:
- periorbital cellulitis (preseptal cellulitis) is limited to the soft tissues anterior to the orbital septum
- often managed with oral antibiotics
- orbital cellulitis (postseptal cellulitis) extends posteriorly to the orbital septum
- a more serious condition requiring hospitalization and parenteral antibiotics
- complications such as intraorbital abscess formation may require surgical intervention
- endophthalmitis involves an intraocular extension of infection
- requires intraocular antibiotics
- possible choroidal debridement or vitrectomy
Orbital infections represent more than half of primary orbital disease processes . These infections typically present in children and young adults but can affect any age group.
- painful ophthalmoplegia
- reduced visual acuity
Periorbital cellulitis often results from contiguous spread of an infection of the face, teeth, or ocular adnexa. Orbital cellulitis typically occurs as an extension of paranasal sinusitis . Endophthalmitis is most commonly secondary to ocular surgery or penetrating injury.
Urgent imaging is indicated to assess the anatomic extent of disease, including postseptal, cavernous sinus and intracranial involvement; evaluate for sources of contiguous spread, e.g. sinusitis or trauma; and identify orbital abscesses that require exploration and drainage . CT is the imaging investigation of choice as it is:
- readily available at all hours and quick
- ideal for assessing for underlying sinus disease
- will identify a subperiosteal reaction or intracranial extension
Diffuse soft-tissue thickening and areas of enhancement anterior to the orbital septum are seen in periorbital cellulitis. It is very difficult to differentiate between preseptal edema and periorbital cellulitis on CT .
- poor definition of orbital planes
- inflammatory stranding in the intraconal fat
- intraconal or extraconal soft tissue mass
- edema of the extraocular muscles
- intraorbital abscess
- subperiosteal abscess
Findings are often non-specific, though choroidal enhancement may be seen in the early phases.
Rarely performed, as not usually necessary. Like CT, it will identify a subperiosteal abscess as:
- T1: low signal
- T2: high signal
- DWI/ADC: diffusion restriction
- T1 + C: rim enhancement
MRI may occasionally have a role in diagnosing endophthalmitis since the presentation can often be non-specific. Key findings include:
- T2 FLAIR: high signal
- DWI/ADC: diffusion restriction in the affected globe
Treatment and prognosis
Periorbital cellulitis is treated with oral antibiotics. Orbital cellulitis is treated with intravenous antibiotics. However, if a subperiosteal abscess is present, surgical drainage may be necessary .
Complications of orbital cellulitis include :
- superior ophthalmic vein thrombosis
- cavernous sinus thrombosis
- loss of vision
- intracranial abscess