title: Local Variability of Parameters for Characterization of the Corneal Subbasal Nerve Plexus.
abstract: OBJECTIVE
  The corneal subbasal nerve plexus (SNP) offers high potential for early diagnosis of diabetic peripheral neuropathy. Changes in subbasal 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 present study set out to identify factors that might account for this high parameter variability.
  
  
  METHODS
  In three healthy subjects, we used a novel method of software-based large-scale reconstruction that provided SNP images of the central cornea, 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.
  
  
  RESULTS
  The three analyzed images ranged in size from 3.75 mm2 to 4.27 mm2. The spatial configuration of the subbasal nerve fiber networks varied greatly across the cornea and thus caused heavily location-dependent results as well as wide value ranges for the parameters assessed. Distributions of SNP parameter values varied greatly between the three images and showed significant differences between all images for every parameter calculated (p < 0.001 in each case).
  
  
  CONCLUSIONS
  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.
authors: a Translational Centre for Regenerative Medicine, University of Leipzig , Leipzig , Germany .|b Department of Ophthalmology , University of Rostock , Rostock , Germany .
authors: Karsten
authors: K
authors: Winter
authors: a Translational Centre for Regenerative Medicine, University of Leipzig , Leipzig , Germany .
authors: Patrick
authors: P
authors: Scheibe
authors: c Institute for Applied Computer Science, Karlsruhe Institute of Technology (KIT) , Karlsruhe , Germany , and.
authors: Bernd
authors: B
authors: Köhler
authors: d Institute for Applied Computer Science/Automation, Karlsruhe Institute of Technology (KIT) , Karlsruhe , Germany.
authors: Stephan
authors: S
authors: Allgeier
authors: b Department of Ophthalmology , University of Rostock , Rostock , Germany .
authors: Rudolf F
authors: RF
authors: Guthoff
authors: b Department of Ophthalmology , University of Rostock , Rostock , Germany .
authors: Oliver
authors: O
authors: Stachs
mesh_terms: D000328:Adult; D003315:Cornea / Q000294:innervation*; D003929:Diabetic Neuropathies / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D018613:Microscopy, Confocal; D009412:Nerve Fibers / Q000473:pathology*; D009882:Ophthalmic Nerve / Q000473:pathology*
keywords: Confocal laser scanning microscopy; cornea; nerve fiber quantification; subbasal nerve plexus