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 with eyelids matted shut, particularly in the morning 1, 2
- Viral: Watery, serous discharge without matting 1, 2
Conjunctival Reaction Pattern
- Bacterial: Papillary reaction on tarsal conjunctiva 1
- Viral: Follicular reaction on inferior tarsal conjunctiva, which is highly characteristic 1
Lymph Node Involvement
- Viral: Preauricular lymphadenopathy is common, especially with adenoviral infections 1
- Bacterial: Preauricular lymphadenopathy is less common 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 1
- Bacterial: May be associated with bacterial otitis media, sinusitis, or pharyngitis, particularly in children 1
Additional Viral-Specific Findings
- Subconjunctival hemorrhages may be present 1
- Chemosis and eyelid swelling can be prominent 1
- Severe cases may develop pseudomembranes or subepithelial corneal infiltrates 1
Clinical History Clues
Factors Favoring Bacterial Etiology
- Matting and adherence of eyelids on waking 3
- Lack of itching 3
- Absence of prior history of conjunctivitis 3
Factors Favoring Viral Etiology
- Recent upper respiratory infection 1
- Known exposure to someone with "pink eye" 1
- Watery discharge predominance 2
Important Caveats
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 pathognomonic finding. 4
Age Considerations
- Bacterial conjunctivitis is more common in children 2
- Viral and allergic conjunctivitis are more common in adults 2
Red Flags Requiring Urgent Ophthalmology Referral
Regardless of suspected etiology, immediate referral is needed for: 1, 5
- Visual loss or decreased vision
- Moderate to severe pain
- Corneal involvement or opacity
- Severe purulent discharge (consider gonococcal)
- History of herpes simplex virus eye disease
- Immunocompromised state
- Lack of response to therapy after 3-4 days
Management Implications
Viral Conjunctivitis
- Antibiotics provide no benefit and should be avoided 1, 5
- Self-limited, typically resolving within 5-14 days 1
- Supportive care with preservative-free artificial tears and cold compresses 1, 2
- Patient education about high contagiousness for 10-14 days from symptom onset 1
Bacterial Conjunctivitis
- Mild cases are usually self-limited and may resolve without treatment 1
- Moderate to severe cases benefit from 5-7 day course of broad-spectrum topical antibiotic 1
- No specific antibiotic has proven superiority; choose based on convenience and cost 1
- Delayed antibiotic prescribing has similar symptom control as immediate prescribing 2