Distinguishing Fungal Keratitis from HSV Endothelial Keratitis: A Comparative Clinical and Diagnostic Analysis

To differentiate the clinical features of fungal keratitis with predominantly deep stromal and endothelial (FSKE) involvement and HSV Endothelial Keratitis (HEK).

Medical records of patients diagnosed with FSKE or HEK between January 2019 and March 2024 were reviewed. We included cases presenting with predominant posterior stromal infiltrates and endothelial exudates that were later confirmed as fungal etiology by microbiology or confocal imaging. These were compared with confirmed HSV endothelial keratitis, diagnosed clinically and/or by PCR (Polymerase Chain Reaction).

A total of 77 cases were included in the study, of which 45 were of FSKE and 32 of HEK. Hyphate edges, along with satellite lesions and the presence of hypopyon, are more commonly seen in fungal cases (66.6% (FSKE) vs. 3.1%, (HEK) OR = 62.0, p = .0001). Posterior stromal involvement was also significantly higher in fungal cases (46.6% vs. 8.8%, OR = 9.4, p = .001). Exudates over the endothelial surface (Endo-exudates) were defined as fluffy in cases with Fungal keratitis as opposed to HSV, where they were more of multiple dot-like (OR = 4.1, p = .005). An intact epithelium was more frequently noted in HEK (84.3% vs. 60% in FSKE, OR = 3.5, p = .02), with the presence of corneal oedema (46.8% vs. 13.3%, OR = 5.7, p = .001). Sampling of these endo-exudates revealed the presence of fungal filaments in 88.8% of fungal keratitis.

Hyphate edges, satellite lesions, hypopyon, fluffy endothelial exudates, and posterior stromal involvement strongly suggest fungal aetiology, whereas intact epithelium, corneal edema, and dot-like endothelial exudates favour HSV.