Description

• Acute infection of orbital contents posterior to orbital septum, with edema and erythema of conjunctiva and eyelids
• Synonym(s): Postseptal cellulitis

• Differentiating orbital from preseptal cellulitis is the critical diagnostic step.
• Diplopia, proptosis, vision loss, and fever suggest orbital involvement.
• Contrast CT is imaging method of choice.
• Treat with immediate IV antibiotics; ophthalmology referral; monitor frequently for vision loss, cavernous sinus thrombosis, abscess, and meningitis.
• Intraorbital foreign body (FB) may cause delayed orbital cellulitis.

Epidemiology

• More common in winter due to incidence of sinusitis (1)[C].
• No frequency difference between the sexes in adults.
• More common in children; mean age of surgical pediatric cases is 10.1 years; 6.1 years for medical pediatric cases (2).
• Haemophilus influenzae type B (Hib) most common organism prior to the Hib vaccine; Staphylococcus and Streptococcus spp. are also common; >30% of cases are culture negative.
• Incidence of Streptococcus anginosis and methicillin-resistant S. aureus (MRSA) may be rising (3).

Incidence
Orbital cellulitis declined since Hib vaccine was introduced in 1985. In 2000, the incidence per 100,000 in California was 3.5 in whites, 6.1 in blacks, and 3.2 in Hispanics, compared to 6.5 in whites, 10.2 in blacks, and 5.5 in Hispanics in 1990.

Risk Factors

• Sinusitis present in 80–90% of cases (4)[C]
• Orbital trauma or retained orbital FB, ophthalmic surgery
• Dental, periorbital, skin, or intracranial infection, acute dacryocystitis and acute dacryoadenitis

Genetics
No known genetic predisposition

General Prevention

• Appropriate treatment of bacterial sinusitis
• Proper wound care and perioperative monitoring of orbital surgery and trauma
• Hib vaccine
• High index of suspicion if fever present with eyelid and conjunctival erythema

Pathophysiology

• Sinusitis is the major risk factor due to thin medial orbital wall; upper respiratory infections, orbital trauma, orbital FB, orbital and periorbital surgery, and bacteremia are risks.
• Cellulitis in the closed bony orbit causes proptosis, globe displacement, orbital apex syndrome, optic nerve compression, and vision loss.
• Orbital abscess (medial wall common), meningitis, and cavernous sinus fibrosis may occur.

Etiology

• Cultures in adults often grow multiple organisms, but >1/3 of cases have no pathogen recovered (3).
• Most common organisms (1,4)[C]:
  • Staphylococcus aureus,Streptococcus pneumoniae,Streptococcus anginosis
• Less common organisms/precursor causes:
  • Moraxella catarrhalis,H. influenza, Group A β-hemolytic streptococcus, Pseudomonas aeruginosa, anaerobes, phycomycosis (mucormycosis), aspergillosis, Mycobacterium tuberculosis, Mycobacterium avium complex, trichinosis, echinococcus
• Since routine vaccination, H. influenzae B is no longer leading cause of orbital cellulitis (1,4)[B].
• MRSA may be rising; highly variable (3).

Commonly Associated Conditions

• >80% of orbital cellulitis cases result from contiguous sinusitis.
• Trauma and intraorbital FB
• Preseptal cellulitis
• Diplopia
• Orbital apex syndrome, vision loss, abscess, meningitis, or cavernous sinus thrombosis
• Neutropenia and asthma are associated, but relationship is unclear