Conjunctivitis

Key clinical points

• Viral conjunctivitis is the most common infectious form and is usually self-limited.
• Watery discharge and preauricular lymphadenopathy suggest a viral cause; thick purulent discharge suggests bacterial.
• Itching is the hallmark of allergic conjunctivitis.
• Pain, photophobia, or reduced vision are red flags requiring closer evaluation.
• Contact lens wearers with a red eye need prompt evaluation for microbial keratitis.

Distinguishing the causes

Viral conjunctivitis, most often adenoviral, typically causes watery discharge, a follicular reaction, and a tender preauricular node, frequently spreading from one eye to the other. Bacterial conjunctivitis produces thicker, purulent discharge. Allergic conjunctivitis is bilateral and dominated by itching, often with a personal or family history of atopy.

A careful history and slit-lamp examination distinguish these entities and identify vision-threatening mimics.

Red flags and evaluation

Significant pain, photophobia, decreased vision, corneal involvement, or a red eye in a contact lens wearer are warning signs that warrant careful examination for keratitis, iritis, or other serious pathology. Fluorescein staining evaluates the cornea for epithelial defects and dendrites.

Management

Viral conjunctivitis is managed supportively with cool compresses and lubrication, along with strict hygiene to limit its high contagiousness. Bacterial conjunctivitis is often self-limited but may be shortened with topical antibiotics, which are important in contact lens wearers and more severe cases. Allergic conjunctivitis responds to allergen avoidance, cool compresses, and topical antihistamine/mast-cell stabilizers.

Antibiotic-sparing practice is appropriate for clearly viral or allergic disease, and antimicrobial choice should reflect risk factors when infection is suspected.