A 52-year-old male farmer from Maharashtra presents with a 5-day history of left eye pain, photophobia, and blurred vision. He reports a thorn prick injury to the cornea while working in the field 2 weeks ago. On examination, visual acuity is 6/60. Slit-lamp examination reveals a central corneal ulcer with raised, indurated edges, satellite lesions, and a hypopyon. KOH mount of corneal scrapings shows broad, aseptate hyphae with right-angle branching. What is the most appropriate next step in management?

Explanation

## Clinical Diagnosis **Key Point:** The KOH mount finding of broad, aseptate hyphae with right-angle branching is pathognomonic for *Aspergillus* species, the most common fungal cause of corneal ulcer in India. **High-Yield:** Fungal corneal ulcers classically present with: - Indolent course (slow progression over days to weeks) - Raised, indurated edges with satellite lesions - Hypopyon (sterile inflammatory exudate) - History of vegetative matter or agricultural trauma ## Organism Identification | Feature | Aspergillus | Candida | Fusarium | | --- | --- | --- | --- | | Hyphae | Broad, aseptate, 5–10 μm | Pseudohyphae, budding yeast | Septate, narrow, 2–4 μm | | Branching | Right-angle (45°) | Acute angle | Acute angle | | Growth rate | Slow | Slow | Rapid | | Clinical course | Indolent | Indolent | Aggressive | | Geography | Tropical/subtropical | Immunocompromised | Tropical | ## Treatment Algorithm ```mermaid flowchart TD A[Fungal corneal ulcer confirmed]:::outcome --> B{Organism identified?}:::decision B -->|Aspergillus| C[Natamycin 5% topical]:::action B -->|Candida| D[Fluconazole or voriconazole]:::action B -->|Fusarium| E[Voriconazole preferred]:::action C --> F[Oral itraconazole 200 mg BD]:::action D --> G[Oral fluconazole 400 mg OD]:::action E --> H[Oral voriconazole 200 mg BD]:::action F --> I[Monitor for perforation risk]:::outcome ``` **Key Point:** Natamycin is the **gold standard topical antifungal** for *Aspergillus* corneal ulcer because: 1. It is a polyene antibiotic with broad-spectrum fungicidal activity 2. It does not penetrate the cornea well systemically, so topical application is essential 3. Oral itraconazole provides systemic coverage and improves outcomes **Clinical Pearl:** Voriconazole is reserved for *Fusarium* (which is resistant to natamycin) or when *Aspergillus* shows poor response to natamycin. Fluconazole is preferred for *Candida* but is less effective against *Aspergillus*. **Warning:** Do NOT use topical steroids in fungal ulcers — they promote deeper invasion and perforation. Avoid systemic antifungals alone without topical therapy in corneal disease.