Corneal confocal sub-basal nerve plexus evaluation: a review

The aim of this study was to review the most recent data about corneal sub-basal nerve plexus (SNP) evaluated with the use of corneal confocal microscopy (CCM). For this purpose, an electronic search was conducted based on PubMed and Google Scholar and Web of Science databases from 2008 up to the end of 2016. Ninety-eight articles in English were cited, as well as abstracts in other languages, concerning the morphology and function of corneal SNP in various diseases. Changes in corneal SNP as a result of local treatment were also introduced. Figures with scans from confocal microscopy from our Department were included. The main conclusion of this review was that both corneal SNP diminishment and high tortuosity as well as low sensitivity are in principle related to the presence or level of pathology. In addition, increased nerve tortuosity may represent a morphological determinant of nerve regeneration. However, the presented literature shows that SNP changes are not characteristic for one unified corneal pathology; rather, they reflect the non-specific pathological process present in many diseases. Future studies should use automatized biometric software and also examine the effects of new treatments on SNP.