What is the first line of treatment for an adult presenting with conjunctivitis (pink eye)?

First-Line Treatment for Pink Eye (Conjunctivitis) in Adults

For mild bacterial conjunctivitis in immunocompetent adults, observation without antibiotics is appropriate as the condition is typically self-limited, though a 5-7 day course of broad-spectrum topical antibiotics (such as moxifloxacin 0.5% three times daily) can shorten symptom duration by 2-5 days if treatment is desired. 1

Determining the Etiology

The first critical step is distinguishing between viral, bacterial, and allergic causes, as management differs significantly:

Bacterial Conjunctivitis Features:

• Mucopurulent discharge with eyelids matted shut upon waking 2
• Lack of itching 3
• No history of recurrent conjunctivitis 3
• More common in children than adults 2

Viral Conjunctivitis Features:

• Watery discharge 2
• Often bilateral presentation 4
• Preauricular lymph node swelling may be present 4
• Accounts for 80% of acute infectious conjunctivitis cases 3, 4

Allergic Conjunctivitis Features:

• Severe itching is the hallmark symptom 3
• Watery discharge 2
• History of allergen exposure 5

Treatment Algorithm by Severity and Type

Mild Bacterial Conjunctivitis (Most Common Scenario)

Observation is a valid first-line approach since mild bacterial conjunctivitis resolves spontaneously in 1-2 weeks without treatment in immunocompetent adults 1, 3. However, topical antibiotics provide benefits:

• Earlier clinical and microbiological remission on days 2-5 of treatment 1
• Reduced transmissibility and earlier return to work 1
• The choice of antibiotic is empiric—select the most convenient or least expensive broad-spectrum option as no specific antibiotic shows superiority 1

Specific antibiotic options:

• Moxifloxacin 0.5% ophthalmic solution: one drop three times daily for 7 days 6
• Povidone-iodine 1.25% ophthalmic solution may be equally effective when antibiotic access is limited 1

Moderate to Severe Bacterial Conjunctivitis

Immediate action required:

• Obtain conjunctival cultures and Gram stain if gonococcal infection is suspected (copious purulent discharge, marked inflammation, severe pain) 1
• Initiate empiric broad-spectrum topical antibiotics while awaiting culture results 1
• Consider MRSA coverage as methicillin-resistant Staphylococcus aureus is increasingly common in bacterial conjunctivitis 1

Gonococcal or Chlamydial Conjunctivitis

Systemic antibiotics are mandatory in addition to topical therapy 1, 5, 3. These sexually transmitted infections require:

• Aggressive treatment to prevent corneal perforation, scarring, and systemic complications 1
• Evaluation for concurrent urethritis, cervicitis, or pelvic inflammatory disease 1

Viral Conjunctivitis

Supportive care only:

• Artificial tears for comfort 2
• Cold compresses 2
• Topical antihistamine eye drops for symptom relief 2
• Strict hand hygiene and avoidance of sharing towels/pillows to prevent transmission 1, 7

Allergic Conjunctivitis

Topical antihistamines with mast cell-stabilizing activity are first-line treatment 2, 3. Brief courses of topical corticosteroids may be considered for severe inflammation but require monitoring of intraocular pressure 8.

Red Flags Requiring Immediate Ophthalmology Referral

Refer urgently if any of the following are present:

• Visual loss or decreased vision 7, 8
• Moderate to severe pain beyond mild discomfort 7, 8
• Corneal involvement (infiltrate, ulcer, or opacity) 1, 7, 8
• Severe purulent discharge suggesting gonococcal infection 7, 8
• Conjunctival scarring or membrane formation 7, 8
• Lack of response to appropriate therapy after 3-4 days 7, 8
• Recurrent episodes despite treatment 7, 8
• Immunocompromised state 7, 8
• Recent ocular surgery 2
• Vesicular rash on eyelids or nose (suggesting herpes zoster ophthalmicus) 2

Critical Pitfalls to Avoid

• Do not prescribe systemic antibiotics for uncomplicated bacterial conjunctivitis—they offer no advantage over topical therapy 7
• Instruct patients to avoid contact lens wear during active conjunctivitis 1, 6
• Do not use topical corticosteroids without ruling out herpes simplex virus as this can worsen herpetic keratitis 1
• Return in 3-4 days if no improvement to reassess and consider culture-guided therapy 7

Follow-Up Recommendations

• Patients may return to work or school after 24-48 hours of antibiotic treatment if symptoms are improving 7
• Complete resolution typically occurs within 7-10 days with appropriate treatment 8
• If symptoms persist despite therapy, obtain conjunctival cultures to rule out MRSA or atypical organisms 8