A 28-year-old woman presents with a 3-day history of bilateral eye redness, foreign body sensation, and watery discharge. She reports recent upper respiratory tract infection. On examination, she has bilateral conjunctival injection, mild chemosis, and scanty mucopurulent discharge. Preauricular lymph nodes are palpable bilaterally. Cornea is clear. What is the most likely causative organism?

## Clinical Diagnosis: Viral Conjunctivitis (Adenoviral) ### Key Clinical Features **Key Point:** The triad of bilateral presentation, recent upper respiratory infection, and preauricular lymphadenopathy is pathognomonic for viral conjunctivitis, particularly adenoviral infection. **High-Yield:** Adenovirus (serotypes 3, 7, 19, 37) causes epidemic keratoconjunctivitis (EKC) and is the most common cause of viral conjunctivitis worldwide. ### Distinguishing Features of Adenoviral Conjunctivitis | Feature | Adenoviral | Bacterial | Chlamydial | |---------|-----------|-----------|----------| | **Onset** | Acute (1–2 days) | Acute (1–2 days) | Insidious (1–2 weeks) | | **Discharge** | Scanty, watery → mucopurulent | Profuse, purulent | Mucopurulent, chronic | | **Preauricular nodes** | Present (90%) | Absent | Absent or mild | | **Corneal involvement** | Subepithelial infiltrates (EKC) | Rare | Pannus, scarring (chronic) | | **Bilateral** | Yes (often) | No (usually unilateral) | Often unilateral initially | | **URTI history** | Common | No | No | ### Pathophysiology 1. Adenovirus binds to conjunctival epithelium via CAR (coxsackievirus-adenovirus receptor) 2. Triggers innate immune response → lymphocytic infiltration 3. Preauricular lymph node enlargement (reactive hyperplasia) 4. Viral replication causes epithelial damage and subepithelial infiltrates **Clinical Pearl:** Epidemic keratoconjunctivitis (EKC) caused by Ad8, Ad19, Ad37 progresses to corneal involvement (subepithelial infiltrates) in 50% of cases, causing photophobia and reduced vision for weeks to months. ### Management Approach **Key Point:** Viral conjunctivitis is self-limited; treatment is supportive. - Artificial tears and cool compresses - Topical antihistamines for itching (if needed) - **Avoid topical antibiotics** unless secondary bacterial superinfection suspected - **Avoid topical corticosteroids** in uncomplicated cases (risk of herpetic keratitis if HSV involved) - Strict hand hygiene to prevent spread - Avoid contact lens wear during acute phase **High-Yield:** Preauricular lymphadenopathy is the single most useful clinical sign to distinguish viral from bacterial conjunctivitis. [cite:Kanski Clinical Ophthalmology 9e Ch 3]