How do you differentiate between viral and bacterial conjunctivitis?

Differentiating Between Viral and Bacterial Conjunctivitis

The most reliable way to differentiate viral from bacterial conjunctivitis is through assessment of discharge type, laterality pattern, and specific clinical signs, with viral conjunctivitis typically presenting with watery discharge and bacterial conjunctivitis with purulent discharge. 1

Key Distinguishing Features

Viral Conjunctivitis

• Discharge characteristics: Watery discharge 1, 2
• Laterality: Often starts unilaterally but becomes sequentially bilateral 1
• Distinctive signs:
  • Preauricular lymphadenopathy (highly suggestive of viral etiology)
  • Petechial and subconjunctival hemorrhage
  • Follicular reaction of inferior tarsal conjunctiva
  • May have membrane/pseudomembrane formation 1
• Associated factors: Recent exposure to infected individuals, concurrent upper respiratory infection 1
• Course: Self-limited with improvement within 5-14 days 1

Bacterial Conjunctivitis

• Discharge characteristics: Purulent or mucopurulent discharge 1
• Morning presentation: Eyelids often matted shut upon waking 2, 3
• Laterality: Can be unilateral or bilateral 1
• Course:
  • Mild cases are self-limited in adults
  • More severe in children with possible complications 1
  • Most uncomplicated cases resolve in 1-2 weeks 3

Additional Diagnostic Clues

Viral Conjunctivitis

• More common in adults 2
• May have associated corneal epithelial defects or punctate keratitis 1
• Highly contagious, often with history of exposure in school or work settings 1
• May have concurrent upper respiratory symptoms 1

Bacterial Conjunctivitis

• More common in children 2
• Lack of itching (differentiates from allergic conjunctivitis) 3
• No history of previous conjunctivitis episodes 3
• Rapid onset of symptoms 1

Special Considerations

Hyperacute Bacterial Conjunctivitis

• Marked eyelid edema
• Marked bulbar conjunctival injection
• Marked purulent discharge
• Preauricular lymphadenopathy
• May have corneal infiltrate or ulcer (especially gonococcal) 1
• Requires immediate treatment to prevent vision-threatening complications 1

Herpetic Conjunctivitis

• Usually unilateral
• May have vesicular skin lesions
• Can have dendrites on cornea (indicating HSV keratitis)
• Requires specific antiviral treatment 4

Management Implications

• Viral conjunctivitis: Primarily supportive care with artificial tears, cold compresses; strict hygiene to prevent transmission 2
• Bacterial conjunctivitis: Topical antibiotics can shorten duration and allow earlier return to work/school 3
• Gonococcal or chlamydial conjunctivitis: Requires systemic antibiotics in addition to topical therapy 3

Pitfalls to Avoid

1. Misdiagnosing HSV conjunctivitis: Look for dendrites on cornea; inappropriate use of corticosteroids in herpetic disease can lead to vision loss 4

2. Missing gonococcal conjunctivitis: This is a medical emergency requiring immediate systemic therapy to prevent corneal perforation 1

3. Overlooking non-infectious causes: Remember that allergic conjunctivitis presents with itching as the predominant symptom 3

4. Indiscriminate antibiotic use: Viral conjunctivitis will not respond to antibacterial agents, and mild bacterial conjunctivitis is often self-limiting 1

5. Missing signs of serious intraocular conditions: Severe pain, decreased vision, and painful pupillary reaction warrant immediate referral 5

By carefully assessing these clinical features, practitioners can more accurately differentiate between viral and bacterial conjunctivitis, leading to appropriate management decisions and better patient outcomes.