8th December 2023

Orbital cellulitis

Orbital cellulitis is an ophthalmic emergency. It is a sight-threatening condition which occurs when there is a bacterial infection of soft tissues posterior to the orbital septum. This differs from pre-septal cellulitis, where there is infection of the soft tissue anterior to the orbital septum without involvement of the globe or orbit. The infection frequently originates from the paranasal sinuses, pre-septal cellulitis, dental infection, dacryocystitis and trauma. Causative organisms include S.Pneumonaie and S.Aureus. It is more common in children and in immunocompromised states. Patients present with a painful swollen eye, change in vision, fever, malaise and less common features of intracranial spread such as meningism or neurological impairment. Typically, there is a history regarding the source of infection, such as recent dental work or upper respiratory tract infection. Examination shows reduced vision and/or signs of optic nerve dysfunction, eyelid swelling and erythema, conjunctival oedema and injection, proptosis, decreased eye movements associated with pain, and the patient is usually febrile. Patients should also be examined for any signs of intracranial spread, such as meningism or focal neurological signs, and if available, fundoscopy should be carried out.

Image Source: Wikimedia Commons (2011). Orbital cellulitis, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Orbital_cellulitis.jpg (Accessed on: 5  May 2022).

Image Source: Wikimedia Commons (2011). RtmaxobitinfectteethCT, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:RtmaxobitinfectteethCT.png (Accessed on: 5  May 2022).

Investigations include blood tests to assess inflammatory markers, blood cultures if febrile and/or culture of the nasopharynx and conjunctiva -although the yield is low, and imaging (contrast enhanced CT scan of orbit, sinuses and brain). Patients presenting with pre-septal cellulitis will need thorough examination to rule out orbital cellulitis. The table below shows differentiating features between orbital cellulitis and pre-septal cellulitis.

Adapted from Kim HJ, Kersten R. Peri-orbital and orbital cellulitis – Symptoms, diagnosis and treatment | BMJ Best Practice, https://bestpractice.bmj.com/topics/en-gb/734 (accessed 31 May 2022).

Patients suspected of having orbital cellulitis need urgent hospital admission and initiation of empirical intravenous antibiotics, which can be tailored to any positive cultures. Antibiotics should cover for anaerobic infections and also have good penetrance of the CSF to cover for intracranial spread. Prompt imaging should be arranged to assess for any evidence of sinusitis, confirm diagnosis and also assess for intracranial spread or presence of abscesses. Children will be managed under paediatrics, and all patients will require ophthalmology input. If necessary, dental, max-fax or ENT input may also be sought. Complications can be localised to the orbit (optic neuropathy, endophthalmitis, central retinal artery occlusion, subperiosteal abscess, ocular empyema) or intracranial (meningitis, abscess and thrombosis).