Fungal Keratitis Following Agricultural Trauma
Probable Diagnosis
The most probable diagnosis is fungal keratitis (keratomycosis), given the history of ocular trauma with plant material in a farmer, combined with 7 days of progressive symptoms. 1 This presentation is classic for fungal infection, as trauma with vegetable matter is a well-recognized risk factor that should immediately raise suspicion for fungal rather than bacterial etiology. 1
Clinical Features
Key Presenting Signs
The clinical examination should specifically document the following features that distinguish fungal from bacterial keratitis:
Corneal infiltrate characteristics: Look for feathery, irregular margins with satellite lesions (multiple smaller infiltrates surrounding the main ulcer), which are highly suggestive of fungal infection 1
Stromal involvement: Document depth of infiltration, presence of stromal edema, and any evidence of suppuration or necrosis 1
Epithelial defect: Fluorescein staining will reveal the area of epithelial loss, often with irregular borders 1
Anterior chamber reaction: Assess for hypopyon (layered white cells in anterior chamber), cell and flare, or fibrin formation 1
Endothelial plaque: May be visible on the corneal endothelium 1
Critical Historical Features
Delayed presentation (7 days) with progressive symptoms despite any prior antibiotic treatment is characteristic of fungal infection 2, 3
Agricultural exposure with plant material trauma is the single most important risk factor 1, 3
Pain, redness, and photophobia are typical presenting symptoms 2, 4
Investigations
Mandatory Microbiological Workup
Given the history of trauma with vegetable matter, corneal scraping for smears and cultures is absolutely indicated before initiating treatment. 1 The American Academy of Ophthalmology specifically states that cultures are "often helpful for eyes that have an unusual history (e.g., if there has been trauma with vegetable matter)." 1
Perform the following investigations:
Corneal scraping using a heat-sterilized platinum spatula or blade under slit-lamp magnification from the advancing borders of the infiltrate 1
Gram stain and Giemsa stain for immediate microscopic evaluation 1
Fungal culture media: Inoculate Sabouraud dextrose agar and other fungal culture media 1
Bacterial cultures should also be obtained, as mixed infections can occur 1
Important Technical Considerations
Avoid tetracaine as the topical anesthetic due to antimicrobial effects 1
Avoid anesthetics with preservatives to improve culture yield 1
Obtain material from the advancing borders, not just purulent material 1
Do NOT delay scraping and culture - this must be done before initiating antifungal therapy 1
Treatment
Immediate Management
Initiate topical antifungal therapy immediately after obtaining cultures, as fungal keratitis can progress rapidly and cause devastating visual loss. 4, 5
Primary antifungal regimen:
Topical natamycin 5% is the first-line agent for filamentous fungal keratitis (most common with plant trauma) 2, 6
Dosing: Apply hourly around the clock initially, then taper based on clinical response 1
Alternative agents: Topical voriconazole or amphotericin B can be considered based on organism identification and sensitivity 4, 6
Adjunctive Measures
Broad-spectrum topical antibiotics should be added initially until bacterial infection is ruled out 2
Cycloplegic agents (e.g., atropine 1%) for comfort and to prevent posterior synechiae if anterior chamber inflammation is present 1
Avoid topical corticosteroids until the infection is controlled, as they can worsen fungal keratitis 1
Monitoring and Modification
Reassess within 24-48 hours to evaluate response to therapy. 1 Look for:
- Reduced pain and discharge 1
- Sharper demarcation of infiltrate borders 1
- Decreased stromal edema 1
- Initial re-epithelialization 1
If no improvement or worsening after 48-72 hours despite appropriate antifungal therapy:
- Consider systemic antifungal therapy (oral voriconazole or fluconazole) 4, 6
- Reculture to assess for resistance or mixed infection 1
- Urgent ophthalmology consultation for possible surgical intervention 4, 5
Surgical Intervention
Therapeutic penetrating keratoplasty may be necessary for:
- Progressive infection despite maximal medical therapy 4, 5
- Impending or actual corneal perforation 4, 5
- Deep stromal involvement with corneal melting 5
Complications
Vision-Threatening Sequelae
Fungal keratitis has a poor visual prognosis even with appropriate treatment, with potential complications including:
Corneal scarring and opacification: Leading to permanent visual impairment 5, 3
Corneal perforation: Requiring emergency surgical intervention 4, 5
Secondary glaucoma: From chronic inflammation or synechiae formation 1
Endophthalmitis: Extension of infection into the intraocular structures 1
Recurrent infection: Occurs in up to 47% of cases even after therapeutic keratoplasty 5
Graft failure: If therapeutic transplant is performed, with rejection rates around 18% 5
Evisceration or enucleation: Required in severe, uncontrolled cases 5, 6
Phthisis bulbi: End-stage ocular degeneration from catastrophic infection 5
Critical Pitfall
The most common error is treating presumed bacterial keratitis with antibiotics alone when fungal infection is present, leading to delayed diagnosis and worse outcomes. 2, 3 The 7-day history of progressive symptoms despite presumed antibiotic treatment in this case is highly suspicious for this scenario. Always obtain cultures when there is trauma with vegetable matter before initiating treatment. 1