Management of Filamentous Fungal Keratitis: A Pragmatic Approach

Abstract

Filamentous fungal infections of the cornea known as filamentous fungal keratitis (FK) are challenging to treat. Topical natamycin 5% is usually first-line treatment following the results of several landmark clinical trials. However, even when treated intensively, infections may progress to corneal perforation. Current topical antifungals are not always effective and are often unavailable. Alternatives topical therapies to natamycin include voriconazole, chlorhexidine, amphotericin B and econazole. Surgical therapy, typically in the form of therapeutic penetrating keratoplasty, may be required for severe cases or following corneal perforation. Alternative treatment strategies such as intrastromal or intracameral injections of antifungals may be used. However, there is often no clear treatment strategy and the evidence to guide therapy is often lacking. This review describes the different treatment options and their evidence and provides a pragmatic approach to the management of fungal keratitis, particularly for clinicians working in tropical, low-resource settings where fungal keratitis is most prevalent.

Keywords: antifungals; chlorhexidine; fungal keratitis; management; microbial keratitis; microbiology; natamycin.

Figure 1

Forest plot of topical natamycin 5% versus voriconazole 1% (outcome: best spectacle corrected visual acuity, logMAR). Reproduced from FlorCruz NV, Evans JR. Medical interventions for fungal keratitis. The Cochrane Database of Systematic Reviews 2015; 4: CD004241 with permission from John Wiley and Sons [5].

Figure 2

Forest plot of topical natamycin 5% versus voriconazole 1% (outcome: corneal perforation). Reproduced from FlorCruz NV, Evans JR. Medical interventions for fungal keratitis. The Cochrane Database of Systematic Reviews 2015; 4: CD004241 with permission from John Wiley and Sons [5].

Figure 3

Forest plot of topical natamycin 5% versus chlorhexidine 0.2% (outcome: clinical cure). Reproduced from FlorCruz NV, Evans JR. Medical interventions for fungal keratitis. The Cochrane Database of Systematic Reviews 2015; 4: CD004241 with permission from John Wiley and Sons [5].

Figure 4

Progression of Fusarium fungal keratitis in a Tanzanian patient despite prompt treatment with topical natamycin 5%. First photograph, baseline presentation; second photograph, progression of infiltrate and increasing hypopyon at one week despite admission and intensive natamycin 5% treatment; third photograph, corneal perforation at three weeks following presentation.

Figure 5

Suggested treatment protocol for filamentous fungal keratitis. * Topical Natamycin 5% is first-line treatment but chlorhexidine 0.2% can be given if natamycin is unavailable. ** Targeted injection refers to either intrastromal/intracameral voriconazole/amphotericin B. *** Perforation includes descemetocele, impending, and frank corneal perforations. Adapted from the TST Protocol [76].