Bacterial Keratitis Corneal Ulcer - Treatment

Key Points

• Corneal infiltrate plus overlying epithelial defect should be treated as microbial keratitis until proven otherwise.
• Contact-lens wear, especially overnight or with water exposure, is a major risk factor for aggressive gram-negative infection.
• Culture large, central, deep, atypical, chronic, postoperative, or treatment-resistant ulcers.
• Begin intensive topical antibiotics promptly; severe disease may require fortified therapy rather than routine outpatient drop frequency.
• Do not patch the eye and do not prescribe repeated topical anesthetic for home use.
• Topical corticosteroids are specialist-directed adjuncts after antimicrobial therapy is established and fungal or Acanthamoeba infection is not suspected.
• Follow-up within about 24 hours is important because corneal melt and perforation can evolve rapidly.
• Failure to improve should trigger repeat culture, adherence review, and reconsideration of fungal, Acanthamoeba, herpetic, or resistant infection.

Algorithm

1. Assess visual acuity, contact-lens history, trauma, water exposure, steroid use, and immune status.
2. Perform fluorescein and slit-lamp examination to document epithelial defect, infiltrate size, depth, and anterior-chamber reaction.
3. If the ulcer is central, large, deep, atypical, postoperative, chronic, or severe, obtain corneal scraping for smear and culture.
4. Start frequent topical fluoroquinolone or fortified antibiotics according to severity and local ophthalmology protocol.
5. Stop contact-lens wear, avoid patching, and add cycloplegia and systemic analgesia when needed.
6. Arrange urgent ophthalmology or corneal-specialist review, generally within 24 hours or immediately for severe disease.
7. Reassess infiltrate, epithelial defect, vision, and anterior chamber; narrow or modify therapy based on microbiology and response.
8. Escalate for corneal thinning, perforation, progression despite therapy, or inability to administer treatment reliably.

Clinical Synopsis & Reasoning

Bacterial keratitis, often called a bacterial corneal ulcer when an epithelial defect overlies stromal infiltrate, is a sight-threatening infection of the cornea. Typical symptoms include pain, photophobia, tearing, foreign-body sensation, discharge, and reduced vision. Examination shows a focal or multifocal corneal infiltrate, epithelial defect on fluorescein staining, surrounding edema, anterior-chamber cells or hypopyon, and conjunctival injection. The infection can progress over hours, particularly with Pseudomonas aeruginosa, Neisseria species, virulent gram-negative organisms, or delayed therapy.

Contact-lens wear is a major risk factor, especially overnight wear, poor hygiene, water exposure, and extended-wear lenses. Other risks include corneal trauma, ocular-surface disease, dry eye, topical corticosteroid use, prior surgery, neurotrophic cornea, and immunosuppression. Agricultural or vegetative trauma broadens the differential to fungal keratitis. Pain out of proportion, ring infiltrate, and water exposure can suggest Acanthamoeba. Dendritic epithelial lesions suggest herpes simplex rather than primary bacterial disease.

The 2024 AAO Bacterial Keratitis Preferred Practice Pattern supports culture and smear for ulcers that are large, central, deep, chronic, atypical, sight-threatening, associated with prior surgery, or unresponsive to empiric treatment. Small peripheral non-sight-threatening ulcers in a reliable patient may be treated empirically without culture. Corneal scraping should precede antibiotics when feasible in severe disease, but therapy should not be delayed for laboratory logistics. A contact lens and case can be cultured selectively, although corneal specimens are more clinically important.

Treatment Strategy & Disposition

Start frequent topical antibiotics immediately. A fourth-generation fluoroquinolone such as moxifloxacin or gatifloxacin is commonly used as monotherapy for many uncomplicated ulcers, often with very frequent initial dosing. Large central, deep, rapidly progressive, or resistant infections may be treated with fortified antibiotics such as topical vancomycin plus tobramycin or ceftazidime according to local corneal-specialist protocols and culture results. Gonococcal disease requires systemic ceftriaxone and urgent specialist management in addition to local therapy.

Cycloplegic drops reduce ciliary spasm and photophobia when anterior inflammation is significant. Systemic analgesia may be required. Stop contact-lens use and discard or disinfect lens supplies as directed. Do not patch an infected cornea. Topical anesthetic should not be prescribed for unsupervised repeated use because it impairs healing and can mask worsening disease. Topical corticosteroids are not started casually at presentation. In selected bacterial ulcers, a corneal specialist may introduce a steroid after effective antibiotics have been established, the organism is responding, and fungal or Acanthamoeba infection is not suspected.

Follow-up is usually within 24 hours for clinically important ulcers and can be even sooner for severe disease. Document infiltrate size, epithelial-defect dimensions, depth, anterior-chamber reaction, and visual acuity so progression can be recognized. Admission may be necessary for threatened perforation, inability to self-administer hourly drops, severe monocular disease, concern for nonadherence, or rapidly progressive infection. Corneal thinning or perforation can require tissue adhesive, therapeutic contact lens, amniotic membrane, or urgent keratoplasty.

Epidemiology / Risk Factors

• Contact-lens-associated disease is a major cause of bacterial keratitis in developed settings.
• Trauma and ocular-surface disease contribute substantially in non-contact-lens users.
• Pseudomonas is especially associated with contact-lens wear, while staphylococci and streptococci are common across multiple risk groups.
• Visual morbidity is concentrated in central, deep, delayed, and virulent infections.

Investigations

Red Flags

Pharmacology

Prognosis / Complications

• Small peripheral ulcers treated promptly often heal with little visual consequence.
• Central stromal scarring can permanently reduce acuity even when infection is eradicated.
• Delayed therapy, deep stromal involvement, resistant organisms, fungal or Acanthamoeba infection, and perforation worsen prognosis.
• Recurrence is uncommon when the infection clears and modifiable risk factors such as contact-lens hygiene are corrected.

Patient Education / Counseling

• Stop contact-lens wear immediately and do not reuse the current lenses or case until ophthalmology provides instructions.
• Explain that the first 24 to 48 hours of drop adherence can determine whether the ulcer stabilizes or progresses.
• Warn against sleeping in lenses, exposing lenses to tap water, showering or swimming in lenses, and topping off old disinfecting solution.
• Provide urgent return precautions for worsening pain, increasing white corneal opacity, new hypopyon, reduced vision, or inability to take the prescribed drops.
• Explain that vision can remain blurred after infection resolves because corneal scarring may persist.

Notes

The article should distinguish ordinary conjunctivitis from microbial keratitis. A patient with a corneal infiltrate and epithelial defect has a different disease with a different urgency. Sending the patient home with routine conjunctivitis drops and no next-day eye follow-up risks corneal melt and permanent visual loss.

Culture strategy should also be severity based rather than universal. AAO guidance supports empiric treatment of some small peripheral ulcers, while central, large, deep, atypical, postoperative, or unresponsive disease deserves microbiologic sampling. That approach preserves speed without sacrificing diagnostic precision in the cases where culture results are most likely to change care.

References

1. American Academy of Ophthalmology Bacterial Keratitis Preferred Practice Pattern — Link
2. AAO Bacterial Keratitis Summary Benchmarks — Link