A 52-year-old farmer from rural Maharashtra presents with a 2-week history of corneal ulcer with stromal infiltration and hypopyon. Gram stain of corneal scrapings shows branching filamentous organisms. Which is the most common fungal organism responsible for corneal ulcers in India?

Explanation

## Fungal Corneal Ulcers in India **Key Point:** *Fusarium* species is the most common fungal cause of corneal ulcers (fungal keratitis) in India and other tropical/subtropical regions, accounting for approximately 40–60% of cases in large Indian series. ### Epidemiology & Risk Factors **High-Yield:** Fungal keratitis is more prevalent in tropical and subtropical regions like India due to: - High humidity and temperature favoring fungal sporulation - Agricultural trauma (plant material, vegetative matter contamination) — the classic risk factor - Immunocompromised states (diabetes, chronic corticosteroid use) The clinical vignette — a **rural farmer** with **corneal ulcer following presumed agricultural exposure**, **branching filamentous organisms on Gram stain**, stromal infiltration, and hypopyon — is the prototypical presentation of *Fusarium* keratitis. ### Comparative Features of Common Fungal Keratitis Pathogens | Feature | *Fusarium* | *Aspergillus* | *Candida* | |---------|------------|---------------|-----------| | **Prevalence in India** | Most common (filamentous) | Second most common | Less common (yeast) | | **Morphology** | Septate branching hyphae | Septate hyphae (45° branching) | Pseudohyphae/yeast | | **Stromal involvement** | Rapid spread, feathery edges, satellite lesions | Dense gray-white infiltrate | Superficial | | **Hypopyon** | Common | Common | Rare | | **Typical setting** | Agricultural trauma, tropical | Tropical, immunocompromised | Immunocompromised, contact lens | ### Gram Stain Findings - *Fusarium*: septate, branching filamentous hyphae — matches the stem description - *Aspergillus*: also septate with acute-angle (45°) branching — can look similar - *Candida*: pseudohyphae and budding yeast — NOT branching filamentous - *Cryptococcus*: encapsulated yeast — NOT filamentous ### Why *Fusarium* and Not *Aspergillus*? While *Aspergillus* is the second most common cause of fungal keratitis in India, multiple large Indian studies (including those from Aravind Eye Hospital, LV Prasad Eye Institute, and AIIMS) consistently identify *Fusarium* species as the **most common** filamentous fungal pathogen in corneal ulcers, particularly in agricultural workers in tropical India. Option D (*Aspergillus fumigatus*) is the most common distractor but is definitively ranked second in Indian epidemiology. ### Treatment **Clinical Pearl:** First-line treatment for filamentous fungal keratitis (including *Fusarium*) in India is **Natamycin 5% eye drops** (the only topical antifungal approved for ocular use). Voriconazole is used as second-line or for deep/refractory cases. *Candida* keratitis responds better to fluconazole or amphotericin B. **High-Yield:** *Cryptococcus neoformans* is primarily a systemic pathogen in immunocompromised patients and is an extremely rare cause of keratitis — essentially a distractor here. [cite: Khurana Ophthalmology, 6th Ed., Ch. 3; Garg's Clinical Ophthalmology; Srinivasan M, Cornea 1997; Thomas PA, Indian J Med Microbiol 2003]