The Evaluation of Corneal Innervation Using Corneal Confocal Microscopy

Corneal confocal microscopy (CCM) is a novel noninvasive method enabling morphological evaluation of corneal structures including nerve fibers. These fibers are almost exclusively of A-delta and C type, i.e. small unmyelinated and poorly myelinated. CCM is thus used as a diagnostic tool for peripheral neuropathies and in particular small fiber neuropathy. The aim of this study was to introduce this method into clinical practice in the Czech Republic, to set-up appropriate normative data and to verify reproducibility of the method. Material and methods: A group of 71 healthy controls was examined using the CCM. The data were used to set normal values in three distinct age-related groups and compare these with CCM findings in a group of 54 patients with diabetic polyneuropathy (DPN). Fully-automated as well as expert manual analysis (by two evaluators) were used for quantification of nerve fiber densities, length and branches to verify reliability of the results. Results: CCM evaluation was easy, well-tolerated and time-efficient in the majority of patients/controls. Age-related normal values showed very good applicability in evaluated groups of healthy individuals and DPN patients. Compared to healthy controls, DPN patients showed highly significant changes of all the evaluated CCM parameters. Results by the two evaluators of the expert manual analysis showed very good reliability, while results from the automated analysis showed significantly lower values on the majority of the CCM parameters. Conclusion: The present study proved on a rather large cohort of healthy controls and a smaller sample of DPN patients that CCM is a easy to use, safe and reliable approach to evaluating corneal innervation. The data also highlighted the differences between automated analysis expert manual CCM analysis.