Feasibility of confocal laser scanning microscopy with slit-lamp microscope in the diagnosis of filamentous fungal corneal infection with culture negative patients

Objective

To investigate the imaging manifestations of different filamentous fungal strains under the confocal laser scanning microscope and slit-lamp microscope, and evaluate the feasibility of rapid diagnosis and therapeutic efficacy judgment for fungal culture negative patients.

Methods

A diagnosis trail was performed.Nine hundred and ninety-three patients with fungal keratitis (FK) which were varified by fungal culture were included in Henan Eye Hospital from September 2013 to January 2014.Distribution of fungi strains and positive rate of fungal strains by fungal culture and corneal confocal laser scanning microscopy were compared.The imaging characteristics of different filamentous fungi and different stages of one filamentous fungi under the slit-lamp microscope and confocal laser scanning microscopy were summarized.

Results

In the 993 FK patients, the diagnostic positive rate of fungal culture and confocal laser scanning microscopy was 43.20% and 82.07%, respectively, showing a significant difference between them (χ²=45.323, P=0.000). In 429 culture-positive patients, the diagnostic positive rate of confocal laser scanning microscopy was 92.31%; while in 564 culture-negative patients, the diagnostic positive rate of confocal laser scanning microscopy was 74.29%.In 429 culture-positive patients, Aspergillus was the most common genus, accounting for 50.12%, and followed by Fusarium sp.and Altemaria sp. (18.18% and 10.49%). There were no significant differences in fungal species distributions between fungal culture and confocal laser scanning microscopy examination in 429 cases (all at P>0.05). The imaging characteristics under the slit-lamp microscope and confocal laser scanning microscope were different in different fungi stains.Aspergillus infection showed a plume-like corneal ulcer, and the Aspergillus sp.hyphae were thin and line-shaped with high reflective light and less branched under the confocal laser scanning microscope.Toothpaste-like corneal infiltrationwas seen in Fusarium sp.-infectiouslesions under the slit lamp microscope, and mycelium showed a high-reflective long rod-like image with less branch in the image of confocal laser scanning microscope.Alternaria alternate sp. corneal infection showed nevus lesions, and hyphae characterized by high-reflective long rod or string beads in shape with less branches in the image of confocal laser scanning microscope.The mycelium was ruptured, shorter, thinner with weak reflective light following drug therapy.The differential diagnosis could be easily obtained between hyphae and corneal nerve fibers by confocal laser scanning microscope.Hyphae intertwined, or had branches with diffuse distribution, which surrounded by high-reflective inflammatory cells and destructed matrix fiber and were located in stroma.The corneal nerve fibers located between epithelium layer and stroma layer, surrounded by normal epithelium or stroma structure.The diameter of the thicker nerve fibers in the stroma layer was obviously thicker than that of the hyphae.

Conclusions

The diagnosis rate of confocal laser scanning microscope combined with slit-lamp microscope for filamentous fungi-infectious FK is higher than that of fungal culture.The combination procedure of confocal laser scanning microscope and slit lamp microscope examination provides a rapid evaluation for fungi strains and therapeutic efficacy in the FK patients with negative results by fungal culture.