Ophthalmic Antibiotics: Practical Selection for Common Presentations
What this page helps you do
Use this guide to select a topical ophthalmic antibiotic based on the presentation, likely organisms, contact lens status, and ocular surface tolerance. The goal is to treat suspected bacterial disease promptly while avoiding unnecessary broad coverage when a narrower option is appropriate. It also highlights scenarios where keratitis requires intensive therapy, culture, or referral.
Common situations and typical starting choices
Start by matching the antibiotic to risk profile and likely pathogens, then refine based on exam findings, history, and local resistance patterns.
- Uncomplicated bacterial conjunctivitis: Polymyxin and trimethoprim drops are a common first choice, especially in pediatrics. In low-risk adults, an older fluoroquinolone can be a cost-conscious alternative in many settings.
- Lid margin disease or bedtime coverage: Erythromycin ointment is commonly used for nocturnal dosing and surface protection, and it is often practical in children.
- Contact lens wear or corneal involvement: Choose an agent with strong gram-negative coverage. Newer fluoroquinolones are commonly used when monotherapy is reasonable.
Fluoroquinolones: when they fit best
Fluoroquinolones are widely used because they provide broad coverage and good corneal penetration. They are often selected when the cornea is involved, in contact lens wearers, or when gram-negative coverage is a priority.
- Older generation: Ciprofloxacin and ofloxacin remain useful and are often cost-effective choices for many external infections, though resistance among staphylococcal species can be higher in some regions.
- Newer generation: Moxifloxacin, gatifloxacin, and besifloxacin provide stronger gram-positive coverage and are commonly used for higher-risk presentations, surgical prophylaxis, and contact lens-related cases where monotherapy is appropriate.
Choose within the class based on local guidance, resistance trends, formulary coverage, and surface tolerance rather than assuming all agents perform the same in every scenario.
Other commonly used options
Several additional topical classes are used frequently for external infections, lid margin disease, and situations where an ointment is preferred.
- Aminoglycosides: Tobramycin and gentamicin offer strong gram-negative coverage. Epithelial toxicity is more likely with frequent dosing and longer courses. Tobramycin is often better tolerated than gentamicin and is common in external regimens and combination products.
- Polymyxin and trimethoprim: Broad coverage for many common external infections and a frequent first choice for pediatric bacterial conjunctivitis.
- Macrolides: Erythromycin ointment remains common for children and bedtime coverage. Azithromycin is sometimes used in lid disease where anti-inflammatory effects may also help.
Suspected microbial keratitis
Suspected bacterial keratitis requires prompt and intensive therapy to achieve bactericidal concentrations in the cornea. Small peripheral ulcers are often started on a newer fluoroquinolone at frequent intervals, especially in contact lens wearers where gram-negative coverage is important.
Larger, central, or vision-threatening ulcers often warrant culture, short-interval follow-up, and co-management with a corneal specialist. Fortified antibiotics from a compounding pharmacy may be appropriate depending on severity and local protocols. Local resistance patterns and referral pathways should guide the regimen and review schedule.