Author: Claude (AI), from PubMed abstracts · Reviewed by: Dr Mina Abdelmseih · Reviewed: 2026-11-15 · Review due: 2027-11-15

Educational content only. Not personalised medical advice. Clinical decisions remain the responsibility of the treating clinician.

Fungal keratitis

Fungal keratitis is a severe corneal infection that often results in blindness and eye loss, most prevalent in tropical and subtropical climates and frequently affecting young agricultural workers of low socioeconomic status [S3]. It probably affects over a million people each year, and 8 to 11% of patients in three case series lost the eye [S3]. Early diagnosis and treatment can preserve vision [S3].

Key points - The minimum estimated annual incidence is 1 051 787 cases, highest in Asia and Africa [S3]. - Corneal scraping for microscopy and culture is the standard for diagnosis [S4] [S6]. - Topical natamycin is first-line for filamentous fungal keratitis; in a Cochrane review it reduced perforation or therapeutic keratoplasty compared with voriconazole (high-quality evidence) [S1] [S7]. - Inappropriate corticosteroid drops, ineffective antibacterial therapy and diagnostic delay contribute to poor outcomes in low-resource settings [S6]. - Severe or non-responding cases may need intrastromal or intracameral antifungals or therapeutic keratoplasty [S7] [S9].

Evidence last checked: 2026-10-17 (PubMed abstracts).

Red flags

• Corneal ulcer after trauma, especially with vegetable matter or in a farmer. Antecedent trauma is a significant predisposing factor [S4].
• Ulcer on steroid drops or not responding to antibiotics. Inappropriate steroid drops and ineffective antibacterial treatment worsen outcomes [S6].
• Delayed diagnosis. Correct identification of fungal infection is often delayed up to 2 to 3 weeks after presentation [S9].
• Thinning or perforation. Fungal infections have a higher rate of perforation requiring surgery than other infectious causes [S9].
• Contact lens wear. Contact lens use was implicated in nearly half of reported Fusarium keratitis cases [S10].

Recognise it

• Who is at risk. Agricultural workers in tropical and subtropical climates [S3]; people with trauma [S4]; contact lens wearers and patients with diabetes or immunosuppression [S11].
• Organisms. Aspergillus and Fusarium are the most common causes [S4]; yeasts, particularly Candida, also occur [S11]. The Fusarium solani species complex predominated in a review of 163 Fusarium cases [S10].
• Signs. Clinical signs are often non-specific [S11].
• Mimic: Pythium. Pythium insidiosum closely resembles fungal keratitis clinically and on smear; reticular dots, tentacular projections, peripheral furrowing and early limbal spread suggest it [S5].

Confirm it

• Corneal scraping with direct microscopy and fungal culture is required for diagnosis [S6] and is the standard of care [S4].
• Other tools include in vivo confocal microscopy, histopathology [S11], PCR and molecular identification, which is especially useful for rare species [S4] [S9].
• Pythium grows on blood agar or other nutritional agar, which is the gold standard; it shows hyphae on 10% KOH and Gram stain like a fungus [S5].

Manage it

Before acting on this section, check the national and local guidelines, product information and regulatory approvals that apply where you practise. See the medical disclaimer.

Tier A (primary care / no specialist)

• Do not start corticosteroid drops on a corneal ulcer: inappropriate steroids contribute to blindness in low-resource settings [S6].
• Refer every suspected infectious corneal ulcer for scraping and antifungal treatment (see "Refer when").

Tier B (general eye clinic)

1. Scrape for direct microscopy and culture [S6].
2. Topical natamycin first-line [S4] [S7]. In a Cochrane review of 12 trials (10 in India), topical 5% natamycin versus topical 1% voriconazole (as reported in [S1]) gave: - fewer perforations or therapeutic keratoplasties (RR 0.61, 95% CI 0.40 to 0.94; 434 participants; high-quality evidence) [S1]; - more microbiological cure at six days in one trial (RR 1.64, 95% CI 1.38 to 1.94; 299 participants) [S1]; - probably better visual acuity, although the confidence interval included no difference [S1] [S2].
3. Alternatives when natamycin is unavailable include voriconazole, chlorhexidine, amphotericin B and econazole [S7]. Voriconazole is described as the best alternative, especially for non-Fusarium cases [S4].
4. Treatment is intensive and often prolonged; topical drugs are often unavailable and not always effective [S6] [S7]. Dosing frequency is not covered by these abstracts: follow local formularies.

Tier C (specialist centre)

• Intrastromal or intracameral antifungal injection may be used [S7]; cases not responding to topical therapy need more invasive treatment [S9].
• Therapeutic penetrating keratoplasty may be required for severe cases or perforation [S7]; early surgery is advised in refractory cases [S11]. Recurrence after keratoplasty is high [S4].
• Cross-linking. Evidence for safety and efficacy of cross-linking in fungal keratitis is inconclusive [S8].
• Photodynamic therapy is being tried for non-responsive cases before a therapeutic graft [S4].
• Pythium. Antibacterials (0.2% linezolid and 1% azithromycin, as reported in [S5]) have been suggested as first-line on in vitro evidence, with early therapeutic keratoplasty in non-resolving cases [S5].

Refer when

Pitfalls

• Treating a fungal ulcer with steroid or antibiotic drops alone [S6].
• Waiting weeks for a diagnosis: identification is often delayed 2 to 3 weeks [S9].
• Missing Pythium, which looks fungal but is treated differently [S5].
• Assuming contact lens keratitis is bacterial: lens wear was implicated in nearly half of Fusarium cases [S10].

Evidence notes

• Thin primary evidence on this sheet. The fungal-keratitis PubMed sheet contains no primary RCTs with abstracts; the landmark trials (for example the Mycotic Ulcer Treatment Trials) are on the microbial-keratitis sheet and are not cited here. Most sources are narrative reviews (expert opinion).
• The Cochrane trials were of variable quality and generally underpowered; most comparisons rested on one small trial [S1].
• The Fusarium review is based on published case reports, with most cases from the United States, suggesting underreporting from tropical regions [S10].
• Modern detailed guidelines on fungal keratitis diagnosis and management are lacking [S6].
• Not covered by these sources: dosing schedules, duration of therapy, oral antifungals, and prevention after agricultural injury.

Related articles

• Bacterial keratitis
• Acanthamoeba keratitis
• Corneal transplantation: DMEK, DSAEK and DALK

References

See the numbered source list below. Each marker [S#] links to its PubMed and DOI record.