Abstract

Orbital cellulitis

is inflammation of eye tissues behind the orbital septum. It most commonly refers to an acute spread of infection into the eye socket from either the adjacent sinuses or through the blood. It may also occur after trauma.

When it affects the rear of the eye, it is known as retro-orbital cellulitis.

It should not be confused with periorbital cellulitis, which refers to cellulitis anterior to the septum.

Signs and symptoms

Common signs and symptoms of orbital cellulitis include pain with eye movement, sudden vision loss, chemosis, bulging of the infected eye, and limited eye movement. Along with these symptoms, patients typically have redness and swelling of the eyelid, pain, discharge, inability to open the eye, occasional fever and lethargy. It is usually caused by a previous sinusitis. Other causes include infection of nearby structures, trauma and previous surgery.

Causes

Orbital cellulitis occurs commonly from bacterial infection spread via the paranasal sinuses. Other ways in which orbital cellulitis may occur is from infection in the blood stream or from an eyelid skin infection. Upper respiratory infection, sinusitis, trauma to the eye, ocular or periocular infection and systemic infection all increase one's risk of orbital cellulitis.

"Staphylococcus aureus", "Streptococcus pneumoniae" and beta-hemolytic streptococci are three bacteria that can be responsible for orbital cellulitis.

- "Staphylococcus aureus" is a gram-positive bacterium which is the most common cause of staphylococcal infections. "Staphylococcus aureus" infection can spread to the orbit from the skin. These organisms are able to produce toxins which promote their virulence which leads to the inflammatory response seen in orbital cellulitis. "Staphylococcus" infections are identified by a cluster arrangement on gram stain. "Staphylococcus aureus" forms large yellow colonies (which is distinct from other Staph infections such as "Staphylococcus epidermidis" which forms white colonies).

- "Streptococcus pneumoniae" is also a gram-positive bacterium responsible for orbital cellulitis due to its ability to infect the sinuses (sinusitis). Streptococcal bacteria are able to determine their own virulence and can invade surrounding tissues causing an inflammatory response seen in orbital cellulitis (similar to "Staphyloccoccus aureus"). Streptococcal infections are identified on culture by their formation of pairs or chains. "Streptococcus pneumoniae" produce green (alpha) hemolysis, or partial reduction of red blood cell hemoglobin.

Treatment

Immediate treatment is very important for someone with orbital cellulitis. Treatment typically involves intravenous (IV) antibiotics in the hospital and frequent observation (every 4–6 hours). Along with this several laboratory tests are run including a complete blood count, differential, and blood culture.

- Antibiotic therapy – Since orbital cellulitis is commonly caused by "Staphylococcus" and "Streptococcus" species both penicillins and cephalosporins are typically the best choices for IV antibiotics. However, due to the increasing rise of MRSA (methicillin-resistant "Staphylococcus aureus") orbital cellulitis can also be treated with Vancomycin, Clindamycin, or Doxycycline. If improvement is noted after 48 hours of IV antibiotics, healthcare professions can then consider switching a patient to oral antibiotics (which must be used for 2–3 weeks).

- Surgical intervention – An abscess can threaten the vision or neurological status of a patient with orbital cellulitis, therefore sometimes surgical intervention is necessary. Surgery typically requires drainage of the sinuses and if a subperiosteal abscess is present in the medial orbit, drainage can be performed endoscopically. Post-operatively, patients must follow up regularly with their surgeon and remain under close observation.

Prognosis

Although orbital cellulitis is considered an ophthalmic emergency the prognosis is good if prompt medical treatment is received.

Death and blindness rates without treatment

Bacterial infections of the orbit have long been associated with a risk of catastrophic local

sequelae and intracranial spread.

The natural course of the disease, as documented by Gamble (1933), in the pre-antibiotic era,

resulted in death in 17% of patients and permanent blindness in 20%.

Complications

Complications include hearing loss, blood infection, meningitis, cavernous sinus thrombosis, and optic nerve damage (which could lead to blindness).