Orbital cellulitis

What it is

Orbital cellulitis is inflammation of the orbital contents posterior to the orbital septum. It is an ocular and medical emergency. It is common in children, in the elderly and in the immunocompromised.

Causes and risk

It is usually secondary to sinus, facial or tooth infections, or to trauma, and it can also arise from a preseptal cellulitis. It is an exogenous infection from injury or, most commonly, from sinusitis, so a recent injury or flu is asked about. It is one of the causes of unilateral proptosis, after thyroid eye disease, along with trauma and orbital or lacrimal gland tumors.

How it presents

A red, swollen, painful eye of acute onset, with erythema and oedema of the eyelids which can spread onto the surrounding skin, is the presentation that puts orbital cellulitis in the differential alongside allergic reaction. The history taken for orbital cellulitis itself is rapid progression of the periocular erythema. There is proptosis, that is forward displacement of the eye, with ophthalmoplegia and restricted eye movements.

Preseptal and orbital cellulitis are told apart by these findings. Fever is present in the orbital form and may be present in the preseptal form. Lid edema is severe rather than moderate to severe. Conjunctival injection is present rather than absent, and chemosis marked rather than absent or mild. Proptosis and pain on eye movement are present rather than absent. Ocular mobility is decreased rather than normal, and vision is diminished with or without diplopia rather than normal. RAPD may be seen rather than absent. Leukocytosis is marked rather than moderate, and the ESR elevated rather than normal or elevated. The additional finding is sinusitis or a dental abscess in the orbital form and a skin infection in the preseptal form. The optic nerve tests may be dysfunctional in the orbital form, and none of these appear in the preseptal form. A short rule holds the two apart: if the eye moves freely it is preseptal, and if there is pain with proptosis it is orbital.