Staphylococcus aureus, Haemophilus influenzae B, Moraxella catarrhalis, Streptococcus pneumoniae, and beta-hemolytic streptococci are 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 from the skin to the orbit. This organism is able to produce toxins which promotes its virulence, leading 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 when cultured (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. Streptococcal bacteria can invade surrounding tissues, causing the 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. Risk Factors
Risk factors for the development of orbital cellulitis include, but are not limited to:
Recent upper respiratory illness
Sinus infection
Younger age
Retained foreign bodies within the orbit
Trauma
Immunosuppression
Systemic infection
Dental infection

Diagnosis
Early diagnosis of orbital cellulitis is urgent, and it involves a complete and thorough physical examination. Common presenting signs include: a protruding eye (proptosis), eyelid edema (swelling), eye pain, vision loss, inability to move the eye completely (ophthalmoplegia), and fever.
If improvement is noted after 48 hours of IV antibiotics, healthcare professionals 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. Corticosteroids - Complications of orbital cellulitis may arise as a result of swelling from the infection. Because the orbit is a small space, increasing the pressure inside can harm the eye. Steroids are drugs that are used to reduce swelling caused by various illnesses, but they can also weaken the immune systems ability to fight the infection. There is inadequate evidence to draw judgments about the use of steroids in the treatment of orbital cellulitis. More research is needed to inform decision making. 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 devastating outcomes 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%.