The features of in vivo laser confocal microscope images of frequent fungal keratitis

Background

Fungal keratitis is one of primary infectious ocular diseases in China. Conventional diagnostic method is fungal cultivation. In vivo laser confocal microscope is a noninvasive examination of ocular surface. However, the study on features of in vivo laser confocal microscope images of frequent fungal keratitis is still not thorough.

Objective

This study was to analyze laser confocal microscope imaging features of four typical fungal keratitis.

Methods

The clinical data of 65 eyes from 65 patients with fungal keratitis were retrospectively analyzed. The patients were initially diagnosed in Nanjing General Hospital of Nanjing Military Command PLA from January 2007 to November 2011, and laser confocal microscope examination of ocular surface and fungal cultivation were performed. The characteristics of laser confocal microscope images were investigated, including shape and type of hypha, distribution of spores and the relationship of hypha with lesion. The differentiation between fungal hypha and other corneal tissues was summarized.

Results

Fungal cultivation showed that among the 65 patients, Fusarium, Aspergillus, Candida and Alternaria were common pathogenic fungus with the infected proportion 63.0%, 16.9%, 3.0% and 4.6%, respectively, and 12.5% patients were infected by other fungus. In the images of laser confocal microscope, hyphae of Fusarium presented the branch-like high reflective structure in the corneal superficial stromal layer and thinning line shape in the deep stromal layer. Few inflammatory cells were found. The peudohyphae and spores from Candida were seen in corneal superficial and mid stroma layers, with few inflammatory cells and many proliferating stromal fibers in the lesions. The hyphae of Aspergillus presented worm-like, showing the thinner and shorter shapes in comparison with those of Candida. The hyphae of Alternaria were long, straight and thick in shape, and spherical chlamydospores were found on the hyphal tip. The hyphae, subepithelial plexus, dendritic cells, fibrosis of the cornea all showed high reflection under the laser confocal microscope, but evidently differences appeared in shape, distribution and course in corneas.

Conclusions

Hyphae are the main basis to diagnose fungal keratitis and differentiate fungi. As a non-invasive examination method, laser confocal microscope can provide useful information for the early diagnosis and treatment of fungal keratitis in vivo.

[Key words] Keratitis/microbiology; Eye infections, fungal/diagnosis; Microscopy, confocal/methods; Differentiation