Have a patient with erythema and swelling of an orbit of the eye? You must distinguish periorbital from orbital cellulitis as they both have different clinical implications.

Periorbital cellulitis typically presents as erythema and swelling of the orbit. Usually there is some sort of trauma involved.

Orbital cellulitis can present the same way but usually stems from bacterial rhinosinusitis.

There will typically be no visual disturbances with periorbital cellulitis but decreased visual acuity or photophobia is common with orbital cellulitis. With periorbital cellulitis there will be painless EOM’s. On the other hand, orbital cellulitis eye movements typically elicit pain. I have distinguished between the two off this finding alone multiple times.

Patients with orbital cellulitis will also present with chemosis, proptosis, and systemic symptoms such as fever and nausea.

You must distinguish between these two pathologies! Treatment options are different as are the possible complications.