Cytoarchitecture of epithelial inflammatory infiltration indicates the aetiology of infectious keratitis

Purpose: To analyse cytological features of corneal epithelium in infectious keratitis. Methods: One hundred and eighteen patients (53 males and 65 females) diagnosed with acute stage of infectious keratitis (45 viral, 40 bacterial, 23 fungal, 10 Acanthamoeba keratitis) were included in study. We performed retrospective analysis of bright and blue-light slit-lamp photographs and in vivo corneal confocal microscopy scans of the corneal epithelium from five corneal regions (superior, inferior, temporal, nasal and central). Density, morphology of inflammatory cells and their relation to epithelial structures, as well as density of nerve fibres, were evaluated in relation to the keratitis aetiology. Results: We characterized five morphological types of inflammatory cells forming infiltration. Cell and nerve fibre densities showed significant differences between groups, and the most intense inflammatory infiltration was associated with fungal then bacterial, viral and Acanthamoeba keratitis. Additionally, differences in aetiology-specific ratio of round/non-round inflammatory cells were observed. Conclusion: Confocal microscopy analysis in infectious keratitis of various aetiologies revealed quantitative and qualitative differences in inflammatory cell infiltration expressed in different ratio of round/non-round inflammatory cells. In vivo microscopic analysis of both the corneal epithelial layer cytopathology and the cytology of inflammatory infiltration provides a fast and specific differentiation of keratitis aetiology that may increase the accuracy in the selection of the initial treatment.