Accurate identification of periorbital and orbital cellulitis is essential for appropriate treatment. Givner reviewed the characteristics (see accompanying table) and treatment of these two clinical entities.

Sources of periorbital infection can be trauma, including insect bites, or bacteremia. The resultant cellulitis is preseptal, or anterior to the orbital septum, involving a fibrous layer beginning at the periosteum of the skull and extending to the eyelids. Periorbital cellulitis does not progress to orbital cellulitis because of this protective fibrous barrier.

Orbital cellulitis is postseptal and involves the orbit itself. The most common cause is extension of infection from sinusitis, although penetrating trauma causes some cases. The orbit is surrounded by the sinuses. The ethmoid sinus is the most common source of orbital infection because a very thin septum separates it from the orbit. Generally, orbital cellulitis occurs in older children because sinusitis is more common as children reach the preteen years. Orbital cellulitis can cause bacteremia.

The clinical signs help to distinguish periorbital from orbital cellulitis. Periorbital infection causes erythema, induration, and tenderness of the periorbital tissues, with patients rarely showing signs of systemic illness. The latter signs are more likely if the infection results from bacteremia. Orbital cellulitis may have the same signs and symptoms in the periorbital tissue but also results in proptosis, edema of the conjunctiva, ophthalmoplegia, or decreased visual acuity. Because the eyelids usually are swollen shut, computed tomographic (CT) scanning with contrast infusion may be necessary to confirm the diagnosis. Nearby sinusitis generally is evident. Although it is associated with orbital cellulitis, periorbital edema can occur without infection, but this condition can be identified by a lack of induration or tenderness.

The causative organism is related to the pathogenesis of infection. Post-traumatic periorbital cellulitis usually is caused by Staphylococcus aureus or Streptococcus pyogenes. Because Streptococcus pneumoniae is the most common cause of bacteremia in young children, it is also the most common cause of periorbital cellulitis. Haemophilus influenzae type b is becoming a rare cause because of the prevalence of H. influenzae vaccinations. Orbital cellulitis results from the pathogens causing sinus infection, often similar to those causing periorbital infection, but may be polymicrobial.

Givner concludes with treatment recommendations. Uncomplicated post-traumatic periorbital cellulitis usually responds to oral antibiotics, such as cephalexin, dicloxacillin, or clindamycin, that treat gram-positive microbes. If there is evidence of bacteremia, the risk of meningitis may require lumbar puncture. Children should be hospitalized initially for parenteral treatment with ceftriaxone (if they have normal cerebrospinal fluid findings), and vancomycin and ceftriaxone (if they have abnormal spinal fluid findings). Response to antibiotics in children with periorbital cellulitis usually is rapid, and a 10-day course of treatment generally is sufficient.

Orbital cellulitis requires careful examination of the eyes and sinuses. Ampicillin/ sulbactam is a good treatment choice; operative drainage is no longer being done. Patients with a large abscess or significant symptoms may require surgical drainage of the abscess and involved sinuses. Improvement should be noted in all patients within 24 to 36 hours. Those who do not improve should have repeat CT scanning and, possibly, surgery. Three weeks of antibiotic therapy, with at least the first week of therapy being administered parenterally, is required in the treatment of children with orbital cellulitis.