Orbital cellulitis is an infection involving the contents of the orbit (fat and ocular muscles), which is posterior to the orbital septum. Preseptal cellulitis is an infection involving the soft tissues anterior to the orbital septum. Both of these conditions is more common in children rather than adults. Orbital cellulitis can usually be distinguished from preseptal cellulitis by the clinical manifestations (ophthalmoplegia, pain with eye movements, and proptosis) as well as imaging studies. Preseptal cellulitis is typically a mild condition, however, orbital cellulitis can lead to vision loss and even to death in severe untreated cases. If the diagnosis is not clear between preseptal and orbital, the patient should be treated as though they have orbital cellulitis.
The most widespread underlying factor that leads to orbital cellulitis is acute sinusitis, especially ethmoid sinusitis or pansinusitis. Risk factors that are less common include orbital trauma and ophthalmic surgery. In the majority of cases, orbital cellulitis is a polymicrobial infection, with the most commonly identified pathogens being Staphylococcus auerus and streptococci.
Diagnosis of orbital cellulitis should be clinically suspected and can be confirmed with CT of the orbits and sinuses with contrast. With the CT, it is important to distinguish between preseptal and orbital cellulitis. In addition through CT or physical exam (extraocular movements, visual acuity, and proptosis evaluation), it is very important to identify any complications of orbital cellulitis such as subperiosteal or orbital abscess, vision loss (through extension of the infection to the orbital apex or inflammation/ischemia of the optic nerve), as well as intracranial extension of the infection (can lead to epidural abscess or subdural empyema, intracranial abscess, meningitis, or cavernous sinus thrombosis). Radiographic evaluation should be completed in all patients who are difficult to examine fully (such as patients less than 1 year old) and patients who fail to show improvement within 1-2 days after starting therapy. It is recommended to obtain blood cultures from patients with suspected orbital cellulitis prior to initiating antibiotics. If surgery is performed, samples should be Gram stained and for patients with risk factors for fungal and/or mycobacterial infection, by specific stains.
Patients with orbital cellulitis should be treated initially with empiric intravenous broad-spectrum antibiotic treatment with activity against Staphylococcus aureus (including MRSA), streptococci, and gram-negative rods. The antibiotic regimen should include Vancomycin plus one of the following: Ampicillin-sulbactam, Cefotaxime, Ceftriaxone, or Piperacillin-tazobactam. If a cephalosporin is used and there is evidence of intracranial extension, Metronidazole should be added in order to cover for anaerobic organisms. The signs and symptoms of orbital cellulitis should begin to improve within 1-2 days after beginning therapy. If clinical improvement is not evident, repeat radiographic evaluation should be completed and surgical evaluation should be considered. In patients with orbital cellulitis that is not complicated, antibiotics should be utilized until all signs of the cellulitis have resolved. The antibiotic regimen should be for a minimum of 2-3 weeks (including both intravenous and oral therapy). There have been no studies completed to define the optimal duration of antibiotic therapy for orbital cellulitis and when to switch from intravenous to oral antibiotics. It is typically accepable to switch to oral antibiotics when the patient is afebrile and the orbital findings have extensively resolved, which is usually within 3-5 days. If there is no culture data available, the following empiric reigmens can be considered: Clindamycin alone; Either Clindamycin or Trimethoprim-sulfamethoxazole plus one of either Amoxicillin, Amoxicillin-clavulanic acid, Cefpodoxime, or Cefdinir
The management of the orbital cellulitis should be multidisciplinatory with consultation with an ENT and ophthalmology team because surgery is sometimes required and may need to be expedited because complications of orbital cellulitis may develop rapidly. Indications for surgery include infection that is poorly responsive to antibiotic therapy, evidence of a large abscess, or decreasing visual acuity.
The prognosis of orbital cellulitis is dependent on whether complications are present. The majority of patients respond rapidly and completely with appropriate therapy. Serious complications, which are rare, are cavernous sinus thrombosis, intracranial extension, and vision loss.