Differentiating Bacterial from Viral Conjunctivitis
Bacterial conjunctivitis characteristically presents with mucopurulent discharge and matted eyelids upon waking, while viral conjunctivitis typically shows watery discharge with a follicular reaction on the inferior tarsal conjunctiva and preauricular lymphadenopathy. 1
Key Clinical Distinguishing Features
Discharge Characteristics
- Bacterial: Purulent or mucopurulent discharge that causes eyelids to be matted shut, particularly in the morning 1, 2
- Viral: Watery, serous discharge without significant matting 1, 2
Conjunctival Reaction Pattern
- Bacterial: Papillary reaction on tarsal conjunctiva 1
- Viral: Follicular reaction, particularly on the inferior tarsal conjunctiva—this is a highly characteristic finding 1
Lymph Node Involvement
- Viral: Preauricular lymphadenopathy is common, especially with adenoviral infections 1
- Bacterial: Preauricular lymphadenopathy is uncommon unless caused by hypervirulent organisms like gonococcus 1
Laterality and Onset
- Viral: Abrupt onset, often starts unilateral but frequently becomes sequentially bilateral within days 1
- Bacterial: Can be unilateral or bilateral at presentation 1
Associated Symptoms
- Viral: Often accompanied by concurrent upper respiratory infection symptoms (cough, sore throat, fever) 1
- Bacterial: May be associated with bacterial otitis media, sinusitis, or pharyngitis, particularly in children 1
Additional Distinguishing Signs
Viral-Specific Features
- Subconjunctival hemorrhages may be present 1
- Chemosis (conjunctival swelling) and eyelid edema/erythema can be prominent 1
- In severe cases, pseudomembranes and subepithelial corneal infiltrates may develop 1
- Self-limited course, typically resolving within 5-14 days 1
Bacterial-Specific Features
- More common in children compared to adults 2
- Eyelids characteristically matted shut upon waking 2
- Less likely to have systemic respiratory symptoms 1
Critical Caveat
No single sign or symptom accurately differentiates viral from bacterial conjunctivitis with 100% certainty 2. The diagnosis relies on pattern recognition using multiple clinical features together rather than any isolated finding. When clinical ambiguity exists, consider that viral and allergic conjunctivitis are more common in adults, while bacterial conjunctivitis predominates in children 2.
Red Flags Requiring Immediate Ophthalmology Referral
Regardless of suspected etiology, refer immediately for: 1
- Visual loss or decreased vision
- Moderate to severe pain
- Severe purulent discharge
- Corneal involvement
- Conjunctival scarring
- Lack of response to therapy
- History of herpes simplex virus eye disease
- Immunocompromised state
- Vesicular rash on eyelids or nose
Management Implications
Avoid indiscriminate use of topical antibiotics, as viral conjunctivitis will not respond to antibacterial agents and unnecessary treatment may cause toxicity 1. For bacterial conjunctivitis with moderate to severe presentation, a 5-7 day course of broad-spectrum topical antibiotic is appropriate, though mild cases are often self-limited 1.