Orbital cellulitis
Overview
Orbital cellulitis is a serious infection of the orbital tissues which can lead to restriction of eye movements, loss of vision and even loss of life. Orbital cellulitis is an inflammation of eye tissues posterior to 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. 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.
Causes
Orbital cellulitis occurs commonly from bacterial infection spread by the paranasal sinuses. Other ways in which orbital cellulitis may occur is from infection in the blood stream and 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 of staph infections. Staphylococcus aureus infection can spread to the orbit from the skin. Staph 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 epidermis 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). Strep organisms 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.
Diagnosis
Orbital cellulitis should be differentiated from preseptal cellulitis which is confined to structures anterior to orbital septum. Where as, orbital cellulitis involves structures posterior to orbital septum which includes fat and ocular muscles.
History and Symptoms
Patients present with sudden onset of fever, proptosis, restricted eye movement, and swelling and redness of the eye lids. It is usually caused by a previous sinusitis.
Physical Examination
Eyes
MRI and CT
Treatment
Because of concern for spread of infection, patients must be admitted to the hospital to receive intravenous antibiotics. The feared complications include cavernous sinus thrombosis and meningitis. Abscess formation is another complication and may require surgical drainage.
Orbital cellulitis is considered an ophthalmological emergency.