A Corneal Ulcer That Is Not Getting Better
A 62-year-old farmer presents with a 10-day history of a painful right eye. He was started on topical ciprofloxacin by a local doctor 7 days ago, but the pain and discharge have worsened. He wears no contact lenses. Acuity is 6/60 right and 6/9 left. There is a 4 mm central epithelial defect with a dense white stromal infiltrate, a 1.5 mm hypopyon, and marked ciliary injection. The corneal sensation is reduced. There is a small area of feathery infiltrate at the leading edge and a plaque-like opacity deep in the stroma. He mentions he was pruning a hedge the week before symptoms began. He is diabetic and on no other medication.
1. Explain why the current treatment is failing and what the likely organisms are.
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Several features point to failure of empirical fluoroquinolone monotherapy.
The history. Outdoor work with plant material is a classic risk for filamentous fungi and for atypical bacteria. Corneal trauma from organic matter should always raise fungal suspicion.
The examination. A feathery leading edge, a deep stromal plaque, reduced sensation, and a slow course despite antibiotics are classic for fungal keratitis. The hypopyon and dense infiltrate indicate severe disease. Reduced corneal sensation also raises the possibility of herpetic disease or a neurotrophic component, but the infiltrate and hypopyon make infection the priority.
Likely organisms. Filamentous fungi - Fusarium and Aspergillus are the commonest in this setting. Atypical bacteria - Nocardia and nontuberculous mycobacteria - can produce a similar indolent picture. Pseudomonas is possible but usually has a more rapid, suppurative course. Herpes simplex virus can cause a geographic ulcer with stromal involvement and reduced sensation, and it can be secondarily infected.
Why the current treatment fails. Ciprofloxacin has poor activity against fungi and many atypical organisms, and it may be poorly penetrating with a deep plaque. Frequent dosing and compliance also matter. The diabetic state impairs healing.
What to do. Stop the current antibiotic, take scrapings for Gram stain, calcofluor white or fungal stain, culture on blood and Sabouraud agar, and consider PCR. Confocal microscopy can help. Do not delay treatment while awaiting results.
2. Outline your management, including the choice of antimicrobials, the role of steroids, and the surgical threshold.
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Initial therapy. Admit or arrange daily review. Start intensive topical therapy with broad cover pending scrapings: fortified vancomycin 5% and fortified tobramycin or ceftazidime 5% hourly around the clock, plus topical natamycin 5% hourly if fungal elements are seen or strongly suspected. If the picture is fungal, natamycin is first-line; voriconazole is an alternative and can be used topically, orally, or intrastromally. For suspected Nocardia, amikacin or sulfacetamide may be added after discussion with microbiology.
Steroids. Do not start topical steroids until the organism is identified, the infection is responding, and there is a clear indication such as persistent inflammation. Steroids in an active fungal ulcer can worsen it. If used, they are started after 48–72 hours of effective antimicrobial cover and under close supervision.
Supportive care. Cycloplegic for comfort and to prevent synechiae. Control diabetes. Analgesia. Monitor hypopyon and anterior chamber daily. Consider B-scan if the view is poor.
Surgical threshold. Therapeutic penetrating keratoplasty is indicated if there is impending or actual perforation, progressive thinning, a non-resolving infiltrate despite appropriate therapy, or a large non-healing ulcer threatening the globe. A conjunctival flap or glue and bandage contact lens can temporise. The decision should be made early in discussion with a cornea specialist, because delay worsens outcomes.
Follow-up. Review daily until the defect is healing and the hypopyon is resolving, then taper antimicrobials slowly over weeks. Warn the patient that fungal ulcers can take months to resolve and that a corneal scar and reduced vision are likely. Address the diabetes and eye protection for future farm work.