Local Variability of Parameters for Characterization of the Corneal Subbasal Nerve Plexus

Abstract

The relatively small size of the conventionally evaluated SNP area is a contributory factor in high SNP parameter variability. 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 the potential for examiner bias when selecting SNP images in the central corneal area.

Comparative quantitative assessment of the human corneal sub-basal nerve plexus by in vivo confocal microscopy and histological staining

“…5 In the present study, we compared local variations of the CNFL parameter in IVCM and histological images by using heat maps. Heat maps are an appropriate tool for the visualization of inhomogeneously distributed elements of the SBP.…”

“…Visual representation of the local variability of respective SBP parameters was attained by generation of heat maps as described earlier. 5 For this purpose, after defining the minimum and maximum values, overlays to the original grayscale images were generated. Minimum value color scale was set to red, whereas the maximum value was set to yellow.…”

“…5 Since IVCM studies consistently underestimate the overall density of the corneal innervation due to its lower resolution compared with IHC, the present study is designed to compare data of SBP parameter local variability, in the context of nerve fiber visibility, from IVCM with ex vivo anatomic data of histologically stained corneas (two different imaging modalities) to validate the differences in parameters related to SBP quantification in healthy human subjects.…”

“…[1][2][3][4] However, the ability of IVCM to adequately resolve intimate details of SBP anatomy remains incompletely understood since the field of view of a conventional IVCM image is relatively small (400 × 400 μm 2 ) and might be insufficient for reliable assessment of SBP morphology. 5 Advancements in imaging extended areas of the corneal SBP by creating large-scale montages [6][7][8] have substantially alleviated this principal limitation of IVCM.…”

“…During the image quantification process, a major point to be considered is intrinsic inhomogeneity of the SBP nerve fiber network pattern which can lead to significant differences among images in various calculated parameters. 5 Immunohistochemistry (IHC) allows studying the anatomical pattern of specific cellular constituents in histological sections and thereby serves as an essential connecting link between basic science and clinical medicine. [14][15][16] IHC has been widely used in the field of ophthalmology to obtain comprehensive anatomical descriptions of human corneal nerve innervation patterns and architecture.…”