Overview
Orbital cellulitis is an ophthalmic emergency. It is a potentially sight- and life-threatening condition in which the tissue behind the orbital septum is infected. The infection usually spreads from surrounding structures, typically from an upper respiratory tract infection such as sinusitis. Periorbital cellulitis can progress to cellulitis.
Causes
The most common pathogens are:
- Staphylococcus aureus
- Streptococcus pneumoniae
- Streptococcus pyogenes
- Haemophilus influenzae – more common in children
Other rarer causes are:
- Fungal infections e.g. mucormycosis/aspergillosis – more common in immunosuppression or diabetic ketoacidosis
Epidemiology
- Both orbital cellulitis and periorbital cellulitis are more prevalent in the winter months due to an increased prevalence of upper respiratory tract infections
- Both orbital cellulitis and periorbital cellulitis are more common in children
Risk Factors
- Sinusitis
- Young age
- Lack of Haemophilus influenzae type B vaccination
- Periorbital cellulitis – can progress to orbital cellulitis
Presentation
Patients usually present with a painful and erythematous eyelid. It can be difficult to distinguish preorbital cellulitis from orbital cellulitis, so it is essential to have a low threshold of suspicion. Any of the following features should raise suspicion for orbital cellulitis:
- Pain with eye movement
- Restrictions in eye movements
- Proptosis
- Visual disturbances
- Chemosis
- Presence of a relative afferent pupillary defect
- Leukocytosis
- Fevers in children
Other features may be:
- Headache
- Malaise
- Features of meningeal involvement – late signs:
- Drowsiness
- Nausea or vomiting
Differential Diagnoses
Periorbital cellulitis
- May be difficult to distinguish
- None of the following are present:
- Pain with eye movement
- Restrictions in eye movements
- Visual disturbances
- Chemosis
- Presence of a relative afferent pupillary defect
- Leukocytosis
- Fevers in children
Thyroid eye disease
- There may be features of hyperthyroidism e.g. heat intolerance, diarrhoea, weight loss
- There may be lid lag on examination
Investigations
All patients
- Immediate referral to secondary care
- FBC and white cell count:
- May show leukocytosis
- CT of the orbits with contrast:
- Diagnostic investigation
- Blood cultures before starting antibiotics
- Shows causative organism
- Microbiology swabs from conjunctiva/nasopharynx/wounds
- Shows causative organism
- If meningeal signs develop: lumbar puncture
- Shows leukocytosis, and positive culture
Management
All patients
- Immediate referral to secondary care
- All patients are managed in hospital due to the risk of intracranial spread
- Do not delay treatment waiting for results
- 1st-line: empirical IV antibiotics
- Options are: cefotaxime or clindamycin or cefuroxime + metronidazole
- Surgery may need to be considered e.g. drainage of orbital abscess
Complications
- Raised intraocular pressure
- Orbital abscesses:
- If the infection spreads to the optic nerve, there can be a total loss of vision
- Intracranial complications:
Prognosis
- Early recognition and treatment carry a better prognosis
- Fungal cellulitis, which is associated with immunosuppression and diabetic ketoacidosis has a higher mortality rate
