Description

• An inflammatory, typically infectious condition affecting the eyelid(s)
• It is anatomically distinguished by its location, isolated to the tissues anterior to the orbital septum:
  • Orbital septum is the connective tissue extension of the orbital periosteum that is reflected into the upper and lower eyelids
  • Extension to the deep tissues is rare because the septum represents a nearly impenetrable barrier but it may be incomplete
• Most commonly presents as a complication of upper respiratory tract infection (URTI) and sinusitis:
  • Swelling is caused by inflammatory edema from vascular and lymphatic congestion
• May occur as a complication of a localized inflammation/infection in the eyelid or adjacent structures:
  • Blepharitis
  • Hordeolum
  • Dacryocystitis
  • Surrounding skin disruptions:
    • Insect bites
    • Minor trauma
    • Impetigo or other dermatologic disorders

• Inflammatory process in the structures deep to the orbital septum
• Typically occurs secondary to extension from an adjacent structure:
  • Sinusitis:
    • Most commonly ethmoiditis penetrating through the thin lamina papyracea
  • Dental abscess
  • Retained foreign body in the orbit
  • Puncture wounds
  • Orbital fracture
  • Postoperative infection
  • Hematogenous spread
  • Rare cause – direct extension of periorbital cellulitis

Etiology

• Streptococcus pneumoniae
• Staphylococcus aureus
• Streptococcus pyogenes
• Moraxella catarrhalis
• Haemophilus influenzae
• Gonococcus – rare
• Consider nonbacterial cause

• Currently streptococcal and staphylococcal infections are the most common causes:
  • S. pneumoniae, Streptococcus viridans, S. pyogenes, Streptococcus anginosus, S. aureus
  • Anaerobes, bacteroides, and gram-negatives may also be seen
• All forms of orbital cellulitis carry a risk of severe morbidity and possible mortality and are therefore a true emergency:
  • Permanent visual loss may occur
  • May extend to subperiosteal space with abscess formation
  • Cavernous sinus thrombosis and CNS infections may be life threatening
• Fungal infections are an uncommon, but an even more lethal form particularly in the immunocompromised:
  • Cerebrorhino-orbital phycomycosis (CROP)
  • Rapidly fatal in 75% of cases:
    • 80% of cases occur in patients with a recent episode of diabetic ketoacidosis
    • Predisposing factor: Severe metabolic acidosis and immunocompromise
    • Begins in the paranasal sinuses and proliferates in the blood vessels causing thrombosis and necrosis
    • Bloody nasal discharge is common
    • May present with evidence of necrosis of the palate and/or nasal mucosa

• Routine vaccination including H. influenzae and Pneumococcus have dramatically decreased periorbital and orbital cellulitis, but infections may still occur with these organisms particularly in younger children and those without at least 2 H. influenzae vaccines
• Periorbital cellulitis is overall 5 times more common and typically occurs in children <5 yr old whereas orbital cellulitis is more common in children >5 yr old