What is the recommended first‑line therapy for acute bacterial conjunctivitis, including specific recommendations for contact lens wearers?

First-Line Therapy for Acute Bacterial Conjunctivitis

For non-contact lens wearers with mild bacterial conjunctivitis, prescribe a 5-7 day course of any broad-spectrum topical antibiotic (gentamicin, tetracycline, ofloxacin, or polymyxin B/trimethoprim), choosing the most convenient or least expensive option; for contact lens wearers, immediately remove lenses and prescribe a topical fluoroquinolone (ofloxacin or moxifloxacin) to cover Pseudomonas species. 1, 2

General Population (Non-Contact Lens Wearers)

Antibiotic Selection

• No single antibiotic demonstrates superiority for uncomplicated bacterial conjunctivitis, so select the most convenient or least expensive broad-spectrum agent 1, 2
• WHO-endorsed first-line agents include gentamicin, tetracycline, or ofloxacin 1, 2
• Polymyxin B/trimethoprim is FDA-approved and effective against common pathogens including Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, and Pseudomonas aeruginosa 3, 4, 5
• Treatment duration: 5-7 days accelerates clinical remission at days 2-5 and allows earlier return to school/work 1

Expected Outcomes

• Topical antibiotics increase clinical remission by approximately 36% at days 2-5 compared to placebo 2
• Without treatment, approximately 41% of patients achieve spontaneous cure by days 6-10 2
• By days 8-10,91% of antibiotic-treated patients versus 72% of placebo patients are cured 4

When Observation Without Antibiotics Is Reasonable

• Mild cases with minimal discharge and no risk factors may be observed, as bacterial conjunctivitis is self-limited 1, 6
• However, antibiotics reduce symptom duration and transmissibility 1

Contact Lens Wearers (High-Risk Population)

Critical First Steps

• Immediately remove contact lenses and discontinue wear until complete corneal recovery is confirmed by an eye-care professional 2, 7
• Perform fluorescein staining to exclude bacterial keratitis before initiating treatment 2, 7

Mandatory Antibiotic Therapy

• Topical antibiotics are required (not optional) in all contact lens wearers due to elevated risk of bacterial keratitis 2, 7
• Fluoroquinolones are preferred (ofloxacin, moxifloxacin, or gatifloxacin) because they provide broader coverage including Pseudomonas species, which are more common in contact lens-related infections 1, 2
• Fourth-generation fluoroquinolones (moxifloxacin, gatifloxacin) offer superior gram-positive coverage including some methicillin-resistant S. aureus strains 1

Red-Flag Signs Requiring Same-Day Ophthalmology Referral

• Moderate to severe pain or unilateral pain 2, 7
• Purulent discharge 2
• Recent water exposure while wearing lenses (swimming, showering, hot tubs) 2, 7
• Photophobia or visual changes 2
• Corneal involvement on fluorescein examination 1

Special Populations Requiring Systemic Therapy

Gonococcal Conjunctivitis

• Systemic antibiotics are mandatory: ceftriaxone 1 g IM single dose plus azithromycin 1 g orally single dose for adults 1
• Add topical therapy and saline lavage for comfort 1
• Obtain conjunctival cultures and Gram staining before treatment 1

Chlamydial Conjunctivitis

• Systemic antibiotics required: oral erythromycin achieves 96% clinical cure and 97% microbiological cure in neonates 2
• Alternative: azithromycin single dose (60% cure) or 3-day course (86% cure) 2
• Topical therapy alone is insufficient 1

MRSA Conjunctivitis

• May require compounded topical vancomycin, as MRSA is resistant to fluoroquinolones and aminoglycosides 1

Follow-Up and Monitoring

When to Schedule Return Visit

• Advise return in 3-4 days if no improvement occurs 1
• Perform visual acuity measurement and slit-lamp biomicroscopy at follow-up 1

Contact Lens Wearer-Specific Follow-Up

• Review contact lens fit, type, and care regimen 7
• Consider switching to daily disposable lenses 7
• Recommend high DK/T ratio (oxygen-permeable) lenses if daily disposables are not feasible 7
• Replace lens cases every 3 months minimum 7

Common Pitfalls to Avoid

In Contact Lens Wearers

• Failing to remove lenses prolongs infection and increases keratitis risk 2, 7
• Omitting fluorescein staining can miss keratitis, potentially causing permanent vision loss 2, 7
• Missing Acanthamoeba keratitis in patients with pain and water exposure history—this requires specialized treatment 7
• Resuming lens wear too early before complete epithelial healing leads to recurrence 7

In All Patients

• Prescribing antibiotics for viral conjunctivitis increases costs and promotes resistance 1
• Using antihistamines for bacterial conjunctivitis provides no benefit, as symptoms are inflammatory (not histamine-mediated) and may delay recognition of treatment failure 1
• Tapering antibiotic doses below 3-4 times daily increases resistance risk 1

Patient Education

Infection Control

• Strict hand hygiene and avoid eye rubbing 1
• Use separate towels and avoid close contact during contagious period 1

Contact Lens Safety

• Never rinse lenses or cases with tap water, bottled water, or homemade saline 7
• Never swim, shower, or use hot tubs while wearing lenses due to Acanthamoeba risk 7
• Overnight wear increases corneal infection risk fivefold compared to daily wear 7