Orbital Infections

Orbital Anatomy & Overview - Stage for Infection

• Orbital Septum: Key fibrous membrane; acts as anterior orbital boundary.

  ⭐ The orbital septum is the key anatomical barrier differentiating preseptal (anterior) from orbital (postseptal) cellulitis.

• Paranasal Sinuses: Close proximity; common primary infection sources.
  • Ethmoid sinus (most common), maxillary sinus.
• Venous Drainage: Valveless veins (e.g., superior/inferior ophthalmic) allow bidirectional flow.
  • Risk of intracranial spread to cavernous sinus.
• Key Spaces: Defined by orbital septum.
  • Preseptal space: Anterior to orbital septum; involves eyelids.
  • Postseptal (Orbital) space: Posterior to septum; involves orbit proper (globe, muscles, optic nerve).

Preseptal Cellulitis - Eyelid's Red Alert

• Definition: Infection of eyelid & surrounding soft tissues anterior to the orbital septum.
• Etiology:
  • Skin trauma (lacerations, abrasions).
  • Insect/spider bites.
  • Spread from hordeolum, chalazion, dacryocystitis.
  • Extension from sinusitis (less common than for orbital cellulitis).
• Common Organisms: Staphylococcus aureus, Streptococcus pyogenes.
• Clinical Features:
  • Eyelid: Edema, erythema, warmth, tenderness.
  • Key Negatives: NO proptosis, NO ophthalmoplegia, NO pain on eye movements.
  • Vision: NORMAL visual acuity, NORMAL pupillary reflexes.

⭐ In preseptal cellulitis, visual acuity, pupillary reactions, proptosis, and ocular motility are characteristically NORMAL.

• Diagnosis: Primarily clinical. CT scan if orbital cellulitis is suspected or if there's no improvement with initial treatment.
• Management:
  • Oral antibiotics (e.g., amoxicillin-clavulanate, cephalexin).
  • Warm compresses.

Orbital Cellulitis - Deep Trouble Eye

• Definition: Infection posterior to orbital septum.
• Etiology: Sinusitis (esp. ethmoiditis), dacryocystitis, dental infection, trauma.
• Organisms: Strep. pneumoniae, Staph. aureus, H. influenzae, anaerobes.
• Clinical Features: Proptosis, painful ophthalmoplegia, ↓ visual acuity, chemosis, APD, fever.
  • Key Differentiators (vs. Preseptal): Proptosis, ophthalmoplegia, ↓VA.
• 📌 Mnemonic (Red Flags - ROPES): Restricted/Painful eye movements, Ophthalmoplegia, Proptosis, Edema/Elevated IOP, Significant vision loss.
• Chandler's: I-Preseptal, II-Orbital, III-Subperiosteal Abscess, IV-Orbital Abscess, V-CST.
• Diagnosis: Urgent CT (orbit & sinuses + contrast). Blood cultures.
• Management:
  • Hospitalize; IV broad-spectrum Abx (Ceftriaxone + Vancomycin; consider anaerobes).
  • Surgery if: abscess, ↓VA, or no improvement in 24-48h.

⭐ The most common cause of orbital cellulitis is extension of infection from adjacent paranasal sinuses, particularly the ethmoid sinus.

Complications & Nasties - When Bugs Go Rogue

• Subperiosteal Abscess (SPA):
  • Collection: bone & periosteum. Location: medial/superior orbit.
  • Drainage: if large, vision threat, or no IV Abx response.
• Orbital Abscess:
  • Pus in orbital fat. ↑ risk vision loss.
  • Management: Usually drainage.
• Cavernous Sinus Thrombosis (CST):
  • Spread: valveless veins.
  • Features: Bilateral signs, CN palsies (III-VI, V1/V2), severe headache, sepsis.
  • Mortality: High. Rx: IV Abx; anticoagulation controversial.
• Fungal Orbital Infections (e.g., Mucormycosis):
  • Form: Rhino-orbital-cerebral.
  • Risk: DKA, immunosuppression, iron overload, post-COVID (India).
  • Features: Black necrotic eschar (nose/palate), rapid progression, multiple CN palsies.
  • Dx: Biopsy (broad, non-septate hyphae, right-angle branching).
  • Rx: Urgent surgical debridement + IV Ampho B.

  ⭐ Rhino-orbital mucormycosis is a life-threatening emergency characterized by black necrotic eschar and requires immediate aggressive surgical debridement and systemic antifungal therapy (Amphotericin B).

High‑Yield Points - ⚡ Biggest Takeaways

• Preseptal cellulitis: Eyelid inflammation, NO proptosis, NO ophthalmoplegia, normal vision.
• Orbital cellulitis: Proptosis, painful ophthalmoplegia, ↓ vision; often from ethmoid sinusitis.
• Common organisms: Staphylococcus aureus, Streptococcus pneumoniae, H. influenzae (in unvaccinated).
• Cavernous Sinus Thrombosis: Critical complication, look for bilateral signs, cranial nerve palsies.
• Management: IV antibiotics (broad-spectrum); surgical drainage for abscess or no improvement.
• Rhino-orbital-cerebral mucormycosis: Aggressive fungal infection in diabetics (DKA); black necrotic eschar.
• Chandler's classification stages orbital complications of sinusitis from preseptal to cavernous sinus thrombosis.