Approach

Differentiation between peri-orbital and orbital cellulitis is imperative as the latter has greater morbidity. Diagnosis of peri-orbital cellulitis is based on history and complete ophthalmological examination. Ophthalmoplegia, proptosis, and visual disturbances are key differentiating factors for orbital cellulitis, and if suspected, a CT or MRI should be ordered to confirm the diagnosis.[20]​ Cultures are usually negative for both, but can be obtained prior to treatment if they are readily accessible. Culture of the nasopharynx and conjunctiva may also be done. However, in most cases, therapy is started empirically.

History

A comprehensive history, along with the pertinent questions about the presenting complaint, should include a history of any recent or current infections (especially of the sinuses, teeth, or ears), styes/chalazions, penetrating injury, and insect bites.[14]​ Underlying sinusitis is the overwhelming cause of orbital cellulitis. In children, it frequently accompanies pre-septal cellulitis as well.[1][21] Any trauma to the eye, direct or indirect (e.g., foreign body in the eye, orbital fracture), should be ruled out. Some patients present with symptoms of this condition after ocular surgery, especially strabismus surgery.[1][9][10][11]​ Haemophilus influenzae type b (Hib) vaccination status should be noted.

Peri-orbital cellulitis usually presents as redness around the eyelid without significant pain, tenderness, swelling, or fever. Orbital cellulitis usually presents as a severe redness around the eyelid that is swollen and tender to touch. Pain (ocular, ear, or facial), malaise, headache, and fever are more common in orbital cellulitis. Nausea/vomiting and drowsiness may indicate meningeal involvement.[1][9][10][11]​​[Figure caption and citation for the preceding image starts]: Swollen and red left eyelidFrom the personal collections of H. Jane Kim, MD, and Robert Kersten, MD, UCSF; used with permission [Citation ends].com.bmj.content.model.Caption@97cbee3

Physical examination

A complete ophthalmological examination should be performed along with a thorough head and neck examination to look for any obvious source of infection such as insect bites to the eye, an infected tooth, or enlarged lymph nodes. Eyelid oedema and erythema are commonly seen in both pre-septal and orbital cellulitis. Visual acuity may be difficult to ascertain in children. It is important to check for a relative afferent pupillary defect, as visual loss due to increased orbital pressure is a real concern in these patients.[1][9][10][11]​​ Intra-ocular pressure may be elevated in orbital cellulitis. This reflects increased orbital pressure due to oedema. Increased orbital pressure can rapidly lead to visual loss and is an indication for urgent intervention. Ophthalmoplegia and proptosis are also key diagnostic factors for orbital cellulitis. Bilateral orbital signs, involvement of the V1 or V2 divisions of the trigeminal nerve, and ophthalmoplegia warrant investigation for cavernous sinus thrombosis. Examine the roof of the mouth and nose for signs of tissue necrosis and a black eschar (late finding) if mucormycosis is suspected (e.g., in immunosuppressed or diabetic patients).

Laboratory investigations

A WBC count, blood cultures and if possible microbiological swab of the conjunctiva, nasopharynx, or any external wound, purulent drainage, or tissue obtained during surgery may be obtained in suspected cases of either peri-orbital or orbital cellulitis.[1][9][10][11]​​[14][15]​​ Positive culture rates are between 0% and 33%.[22] Results are more likely to be positive in children rather than adults.​[21][23]​​​ A lumbar puncture is recommended if meningeal signs develop.[12][13]

Imaging

A CT scan with contrast medium is the mainstay diagnostic method for suspected cases of orbital cellulitis, looking for paranasal sinus disease or sub-periosteal abscess.[1][9][10][11]​​[24]​​​ An MRI may be requested to rule out intracranial abscesses and cavernous sinus thrombosis, if clinically indicated.[12]​ Orbital ultrasonography can differentiate between pre-septal and orbital infection and may have advantages for some patients as it can be performed at the bedside and does not require sedation; however, it is unable to adequately assess associated sinus or intracranial involvement.[19][25]​​[26]​​

Referral

Any patient with evidence of peri-orbital oedema and redness accompanied by visual disturbance should be referred to an oculoplastics consultant.[1][9][10][11]​​

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