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Oliver Stachs, Karsten Winter, Patrick Scheibe, Bernd köhler, Stephan Allgeier, Rudolf F Guthoff; Local variability of parameters for characterization of the corneal sub-basal nervePlexus. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1636.
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The corneal sub-basal nerve plexus (SNP) offers high potential for early diagnosis of peripheral neuropathy. Changes in sub-basal nerve fibers can be assessed in vivo by confocal laser scanning microscopy (CLSM) and quantified using specific parameters. While current study results agree regarding parameter tendency, there are considerable differences in terms of absolute values. The aim of this study is to find indications for this high parameter variability.
We used a novel method of software-based large-scale reconstruction that provided SNP images from three healthy subject's central corneas, decomposed the image areas into all possible image sections corresponding to the size of a single conventional CLSM image (0.16 mm2) and calculated a set of parameters for each image section. In order to carry out a large number of virtual examinations within the reconstructed image areas an extensive simulation procedure (10,000 runs per image) was implemented.
The three analyzed images had a size of 3.75 mm2 to 4.27 mm2. The spatial configuration of the sub-basal nerve fiber networks varied greatly across the cornea and thus caused heavily location-dependent results as well as high value ranges for the assessed parameters. Distributions of SNP parameter values greatly varied between the three images and showed significant differences between all images for every calculated parameter (all p < 0.001).
The high parameter variability contributes to the relatively small size of the conventionally evaluated SNP area in regard to the size of SNP features. Averaging of parameter values based on multiple CLSM frames does not necessarily result in good approximations of the respective reference values of the whole image area. This illustrates a potential examiner bias when selecting SNP images in the central corneal area.
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