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What is it?Orbital cellulitis is a bacterial infection of the periocular tissues. Cellulitis restricted to the soft tissues anterior to the orbital septum (a connective tissue curtain that divides the anterior third from the posterior two thirds of the orbit) is called "pre-septal cellulitis." It is much less serious than infection that extends behind the orbital septum, called "post-septal cellulitis."
The infection usually starts in the paranasal sinuses, especially the ethmoid. It is especially common in children.
Orbital cellulitis is rare in adults, except among the immunocompromiseddiabetes mellitus, chronic immunosuppressive agents, or irradiation. In these patients, the big danger is fungal infectionmucormycosis or aspergillosis. Both are life-threatening fungal infections that require prompt management.
How does it present?Orbital cellulitis presents with periocular pain, violaceous swelling of upper and lower lids, and mild, diffuse conjunctival hyperemia. Fever and upper respiratory infection symptoms may be present in children. The eyelids and globe are tender to the touch. If the infection extends posterior to the orbital septum, there will be reduced ocular movement and proptosis. Visual loss is rare.
In adults, fungal orbital infection originates more posteriorly in the orbit and may show minimal swelling. Ptosis, reduced eye movement, and vision loss are more common.
Delayed treatment can lead to blindness and intracranial spread of infection with meningitis, stroke, and death.
What to do?Order sino-orbital imaging studies to rule out sinusitis, orbital subperiosteal abscess, or tumor. Treat with intravenous antibiotics. Subperiosteal abscess may require surgical drainage.
Lack of improvement in 24 to 48 hours signals either an incorrect diagnosis or ineffective antibacterial agents.
Always think of fungal infections in immunocompromised hosts!