What is the difference between viral conjunctivitis and bacterial conjunctivitis?

Differences Between Viral and Bacterial Conjunctivitis

Viral conjunctivitis and bacterial conjunctivitis can be distinguished by their clinical presentation, associated factors, and treatment approaches, with viral conjunctivitis typically presenting with watery discharge and bacterial conjunctivitis presenting with mucopurulent discharge.

Clinical Presentation

Viral Conjunctivitis

• Discharge characteristics: Watery, serous discharge 1, 2
• Onset: Abrupt onset, often unilateral initially but becoming sequentially bilateral 3
• Conjunctival appearance: Bulbar conjunctival injection, follicular reaction of inferior tarsal conjunctiva, chemosis 3
• Associated symptoms: May have concurrent upper respiratory infection 3
• Lymphadenopathy: May have palpable preauricular lymph nodes, especially with adenovirus 3, 4
• Duration: Self-limited, with improvement within 5-14 days 3

Bacterial Conjunctivitis

• Discharge characteristics: Mucopurulent discharge, eyelids often matted shut upon waking 1, 2
• Onset: Can be acute or subacute
• Conjunctival appearance: Bulbar conjunctival injection, may have papillary reaction
• Associated symptoms: Lack of itching, mattering and adherence of eyelids on waking 2
• Duration: Most uncomplicated cases resolve in 1-2 weeks, faster with antibiotic treatment 2

Causative Organisms

Viral Conjunctivitis

• Accounts for approximately 80% of all acute conjunctivitis cases 4
• Common causative agents:
  • Adenovirus (most common - 80% of viral cases) 4
  • Herpes simplex virus (HSV) 3
  • Varicella zoster virus (VZV) 3
  • Enterovirus 4

Bacterial Conjunctivitis

• Common causative organisms 3, 5:
  • Staphylococcus aureus
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Moraxella catarrhalis
  • Escherichia coli
  • Other Enterobacteriaceae

Diagnostic Considerations

Viral Conjunctivitis

• Clinical diagnosis primarily based on presentation
• Distinctive signs for specific viral causes:
  • HSV: Vesicular rash or ulceration of eyelids, dendritic epithelial keratitis 3
  • VZV: Vesicular dermatomal rash, pseudodendritic epithelial keratitis 3
• Laboratory testing options:
  • Viral culture
  • Nucleic acid amplification tests (NAATs) for specific viruses 3

Bacterial Conjunctivitis

• Clinical diagnosis based on presentation
• Laboratory testing options:
  • Gram stain of conjunctival swab
  • Aerobic bacterial culture 3
  • Important for cases with severe symptoms or in high-risk patients

Treatment Approaches

Viral Conjunctivitis

• Generally self-limiting without specific treatment 2
• Supportive care:
  • Artificial tears
  • Cold compresses
  • Antihistamine eye drops for symptomatic relief 1
• Specific antiviral treatment for HSV conjunctivitis:
  • Trifluridine for dendritic lesions 6, 7
  • Acyclovir, valacyclovir for HSV 7

Bacterial Conjunctivitis

• Topical antibiotics decrease duration and allow earlier return to work/school 2
• Common antibiotic options:
  • Sulfacetamide sodium 10% for susceptible organisms 5
  • Erythromycin ophthalmic ointment 8
• Delayed antibiotic prescribing has similar outcomes to immediate prescribing in uncomplicated cases 1
• Special considerations:
  • Conjunctivitis due to sexually transmitted infections (gonorrhea, chlamydia) requires systemic antibiotics in addition to topical therapy 2

Complications and Prognosis

Viral Conjunctivitis

• Potential sequelae of adenoviral conjunctivitis:
  • Conjunctival/subtarsal scarring
  • Symblepharon
  • Keratitis and dry eye
  • Subepithelial corneal infiltrates
  • Corneal scarring 3

Bacterial Conjunctivitis

• Untreated severe bacterial keratitis can lead to:
  • Corneal perforation
  • Endophthalmitis
  • Vision loss 3, 9

Prevention and Transmission Control

Viral Conjunctivitis

• Highly contagious, especially adenoviral conjunctivitis 4
• Prevention measures:
  • Strict personal hygiene
  • Frequent handwashing
  • Surface sanitization 1, 4

Bacterial Conjunctivitis

• Less contagious than viral, but still transmissible
• Prevention measures:
  • Hand hygiene
  • Avoiding sharing of personal items

Special Considerations

Immunocompromised Patients

• Higher risk for severe infections and complications 9
• May require more aggressive diagnosis and treatment
• Close monitoring recommended for patients with:
  • HIV/AIDS with low CD4+ counts
  • Other immunocompromising conditions 9

When to Refer to Ophthalmology

Immediate referral indicated for:

• Conjunctivitis in neonates
• Severe pain
• Decreased vision
• Recent ocular surgery
• Vesicular rash on eyelids or nose
• History of rheumatologic disease
• Immunocompromised state 1