How to differentiate between viral and bacterial conjunctivitis?

Differentiating Viral from Bacterial Conjunctivitis

Viral conjunctivitis typically presents with watery discharge, follicular reaction on the inferior tarsal conjunctiva, and preauricular lymphadenopathy, while bacterial conjunctivitis characteristically shows mucopurulent discharge with matted eyelids upon waking and a papillary rather than follicular reaction. 1

Key Clinical Differentiators

Discharge Characteristics

• Viral: Watery, clear discharge that does not cause eyelids to stick together 1, 2
• Bacterial: Mucopurulent or purulent discharge with eyelids matted shut, especially in the morning 1, 2

Conjunctival Reaction Pattern

• Viral: Follicular reaction on the inferior tarsal conjunctiva (small, dome-shaped elevations) 1
• Bacterial: Papillary reaction (flat-topped elevations with central vessels) rather than follicular 1

Lymph Node Involvement

• Viral: Preauricular lymphadenopathy is commonly present, particularly with adenoviral infections 1
• Bacterial: Preauricular lymphadenopathy is typically absent unless caused by hypervirulent organisms like gonococcus 1, 3

Onset and Laterality

• Viral: Abrupt onset, often starts unilateral but frequently becomes sequentially bilateral within days 1
• Bacterial: Can be unilateral or bilateral from onset 1

Associated Symptoms

• Viral: Often accompanied by concurrent upper respiratory infection symptoms (sore throat, runny nose, cough) 1
• Bacterial: May be associated with bacterial otitis media, sinusitis, or pharyngitis, particularly in children 1

Additional Viral Features

• Subconjunctival hemorrhages may be present 1
• Chemosis (conjunctival swelling), eyelid swelling, and erythema are common 1
• In severe cases, may develop pseudomembranes or subepithelial corneal infiltrates 1

Critical Red Flags Requiring Immediate Ophthalmology Referral

Document these pertinent negatives to ensure uncomplicated conjunctivitis 3:

• Severe or moderate pain suggests corneal involvement or sight-threatening conditions 3
• Photophobia indicates corneal involvement, anterior chamber inflammation, or viral keratitis (HSV/VZV) 3
• Vision loss or blurred vision suggests corneal involvement or anterior chamber inflammation 3
• Corneal infiltrates, ulceration, or epithelial defects on fluorescein staining indicate bacterial keratitis, which can progress to perforation within 24 hours with virulent organisms 3
• Contact lens use requires different antibiotic coverage and often ophthalmology referral 3
• Vesicular lesions on eyelids suggest HSV or VZV keratoconjunctivitis 3
• Severe, rapidly reaccumulating purulent discharge suggests hyperacute bacterial conjunctivitis (consider gonococcal) 3

Management Implications

For Viral Conjunctivitis

Avoid antibiotics entirely, as they provide no benefit and may cause toxicity. 1

• Supportive care with artificial tears for symptomatic relief 1, 2
• Topical antihistamines for symptomatic relief 1
• Cold compresses 2
• Patient education about high contagiousness: minimize contact with others for 10-14 days from symptom onset 1
• Self-limited course, typically resolving within 5-14 days 1
• Strict hand hygiene with soap and water, avoid sharing towels and pillows 1

For Bacterial Conjunctivitis

Mild bacterial conjunctivitis is usually self-limited, but for moderate to severe cases, prescribe a 5-7 day course of broad-spectrum topical antibiotic. 1

• No evidence demonstrates superiority of any particular topical antibiotic agent 1
• Choose the most convenient or least expensive option 1
• Delayed antibiotic prescribing has similar symptom control as immediate prescribing 2

Common Pitfalls to Avoid

• Do not use topical antibiotics indiscriminately for viral conjunctivitis, as viral cases will not respond to antibacterial agents 1
• Avoid topical corticosteroids unless under ophthalmology supervision, as they can prolong adenoviral infections, worsen HSV infections, and cause increased intraocular pressure and cataracts 1
• Do not miss hyperacute bacterial conjunctivitis (gonococcal), which presents with marked eyelid edema, bulbar conjunctival injection, and copious purulent discharge—this requires systemic treatment and can lead to corneal perforation 1
• Recognize that no single sign or symptom accurately differentiates viral from bacterial conjunctivitis in all cases, so comprehensive clinical assessment is essential 2