Orbital cellulitis is defined as a serious infection that involves the muscle and fat located within the orbit. It is also sometimes referred to as postseptal cellulitis. Orbital cellulitis does not involve the globe itself. Although orbital cellulitis can occur at any age, it is more common in the pediatric population.The causative organisms of orbital cellulitis are commonly bacterial but can also be polymicrobial, often including aerobic and anaerobic bacteria and even fungal or mycobacteria. The most common bacterial organisms causing orbital cellulitis are Staphylococcus aureus and Streptococci species. Rare cases of orbital cellulitis caused by non-spore-forming anaerobes Aeromonas hydrophila, Pseudomonas aeruginosa, and Eikenella corrodens have also been reported. Fungal pathogens causing invasive orbital cellulitis include Mucorales which causes mucormycosis and Aspergillus which can cause life-threatening invasive orbital infections. In immunocompromised patients with orbital cellulitis, mucormycosis and invasive aspergillosis should be considered as the cause of orbital cellulitis. Mucormycosis affects patients with diabetic ketoacidosis as well as the patients with renal acidosis. Aspergillus infection of the orbit occurs in patients with severe neutropenia or other immune deficiencies, such as HIV infection. Other rare reported cause of orbital cellulitis is mycobacteria, especially Mycobacterium tuberculosis.
Orbital cellulitis is primarily diagnosed clinically by objective findings on physical examination combined with presenting signs and symptoms. The most important distinguishing feature of orbital cellulitis is the presence of ophthalmoplegia, the presence of pain with eye movement, and/or proptosis. Orbital cellulitis also typically cause eyelid swelling with or without erythema; however, these findings are also seen in another less serious condition called preseptal cellulitis. The diagnosis of orbital cellulitis can be confirmed by imaging modalities such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). Due to the controversy surrounding imaging use and the risks of radiation exposure to the pediatric population, there are guidelines and recommendation in place that highlight the indications and aid in the proper use of imaging for diagnosis of orbital cellulitis.
Treatment of orbital cellulitis includes antibiotics and other supportive therapies. An ophthalmologist and otolaryngologist should also be consulted for proper examination and because, in some cases, surgery may be required. Without prompt diagnosis and proper treatment, the infection of the orbit can progress and extend to the adjacent anatomical locations and result in serious complications. Those complications include loss of vision, subperiosteal abscess, orbital abscess, and intracranial extension of the infection. The choice of antibiotics is broad spectrum regimens aimed at covering for organisms such as S. aureus (including methicillin-resistant S. aureus [MRSA]), Streptococcus pneumoniae, other Streptococci, as well as gram-negative bacilli. The antibiotic regimen should also include coverage for anaerobes when an intracranial extension is suspected. Antifungals are indicated only when a fungal infection is suspected in the appropriate clinical setting. Further details on specific antibiotics will be explained in the diagnosis section. Analgesics such as NSAIDs and acetaminophen can be used alone or in combination to achieve effective pain control in patients with orbital cellulitis.
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