A 58-year-old diabetic woman from Delhi presents with a 10-day history of progressive left eye pain and blurred vision. Examination reveals a 3 mm corneal ulcer with feathery, raised borders, satellite lesions, and a stromal haze. KOH mount of corneal scrapings shows septate hyphae. What is the most appropriate next step in management?

Question

Accepted Answer

C. Start topical natamycin 5% every 1–2 hours and oral itraconazole 200 mg twice daily; refer to tertiary centre. ## Clinical Context
This patient has a **fungal corneal ulcer** (septate hyphae on KOH mount) with classic features: feathery borders, satellite lesions, stromal haze, and a history of diabetes (immunocompromised state). Fungal ulcers progress rapidly and require aggressive systemic and topical antifungal therapy.

## Fungal Corneal Ulcer: Diagnosis & Management

```mermaid
flowchart TD
  A[Corneal ulcer + risk factors]:::outcome --> B{Clinical clues?}:::decision
  B -->|Feathery borders, satellites, stromal haze| C[Suspect fungal]:::urgent
  C --> D[KOH mount, culture on SDA]:::action
  D --> E{Septate or non-septate?}:::decision
  E -->|Septate hyphae| F[Filamentous fungus]:::outcome
  E -->|Yeast| G[Candida species]:::outcome
  F --> H[Natamycin 5% topical]:::action
  G --> I[Fluconazole or voriconazole]:::action
  H --> J[Oral itraconazole 200 mg BD]:::action
  I --> K[Oral fluconazole 400 mg daily]:::action
  J --> L[Refer to tertiary centre]:::action
  K --> L
  L --> M[Monitor closely, consider debridement if needed]:::action
```

## Key Point:
**Natamycin 5% is the topical agent of choice for filamentous fungal keratitis.** It is the only FDA-approved topical antifungal for corneal ulcers and achieves superior corneal penetration compared to azoles.

## High-Yield:

| Feature | Filamentous Fungus | Candida |  
|---------|-------------------|---------|  
| **Hyphae** | Septate (e.g., *Aspergillus*, *Fusarium*) | Yeast or pseudohyphae |  
| **Topical agent** | Natamycin 5% (hourly) | Fluconazole 1% or voriconazole 1% |  
| **Systemic agent** | Itraconazole 200 mg BD | Fluconazole 400 mg daily |  
| **Borders** | Feathery, raised, satellite lesions | Diffuse, less demarcated |  
| **Stromal involvement** | Deep, with haze | Variable |

**Mnemonic: NATAMYCIN for Filamentous — NAT = Non-Azole Topical**

## Clinical Pearl:
Fungal ulcers in **diabetics** progress rapidly and have a poor prognosis if not treated aggressively. The combination of topical natamycin + systemic itraconazole (which achieves aqueous penetration) is standard. Referral to a tertiary centre is mandatory because:
1. Fungal ulcers often require corneal debridement or therapeutic keratoplasty
2. Risk of perforation is high
3. Requires specialist monitoring and potential surgical intervention

## Warning:
~~Fluconazole or voriconazole alone (topical) is inadequate for filamentous fungal keratitis.~~ While these azoles are effective against *Candida*, they have poor corneal penetration and are NOT first-line for *Aspergillus* or *Fusarium*. Natamycin is superior for filamentous fungi.

~~Corneal debridement as first-line is controversial~~ and should be deferred unless there is impending perforation or after initiation of antifungal therapy. Aggressive debridement may worsen the ulcer.

## Tip:
- **Septate hyphae on KOH** = filamentous fungus → natamycin
- **Yeast or pseudohyphae** = *Candida* → azole (fluconazole or voriconazole)
- Always culture on **Sabouraud dextrose agar (SDA)** for fungal identification and antifungal susceptibility
- Systemic antifungal is essential for stromal involvement
- Tertiary referral is non-negotiable for fungal keratitis

Answer

A. Prescribe topical fluconazole 1% hourly and review in 48 hours

Answer

B. Perform corneal debridement and apply topical miconazole ointment

Answer

D. Start topical voriconazole 1% hourly and oral fluconazole 400 mg daily

Explanation

Clinical Context

Fungal Corneal Ulcer: Diagnosis & Management

Key Point:

High-Yield:

Clinical Pearl:

Warning:

Tip:

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Feature	Filamentous Fungus	Candida
Hyphae	Septate (e.g., Aspergillus, Fusarium)	Yeast or pseudohyphae
Topical agent	Natamycin 5% (hourly)	Fluconazole 1% or voriconazole 1%
Systemic agent	Itraconazole 200 mg BD	Fluconazole 400 mg daily
Borders	Feathery, raised, satellite lesions	Diffuse, less demarcated
Stromal involvement	Deep, with haze	Variable