Analysis of corneal subbasal nerve plexus from wide-area mosaics in healthy subjects and in type 2 diabetics

Abstract

Purpose : Very little is known about the subbasal nerve plexus architecture and density over a wide field of view in type 2 diabetes. We therefore performed a cross-sectional observational study to examine qualitative plexus changes and subbasal nerve density in type 2 diabetes relative to an age- and sex-matched healthy control group.

Methods : Laser-scanning in vivo confocal microscopy (IVCM) with the HRT3-RCM system was performed in 82 subjects bilaterally (39 diabetics and 43 controls). Wide-area mosaics were reconstructed by an automated algorithm and subbasal nerves in all mosaics were traced manually and by a fully automated tracing algorithm. Subbasal nerve density was compared between diabetics and healthy groups and according to diabetes duration.

Results : 163 mosaics from 82 subjects were successfully reconstructed, representing a mean enhancement factor of 37 single confocal fields of view and mean area of 6 mm² of the central cornea. Patterns of innervation of the subbasal plexus could be studied qualitatively, and revealed regional variations in nerve density and tortuosity. Nerve density in the mosaic was highly correlated between manual and fully automated methods of nerve tracing (R² = 0.88, P < 0.001), while the automated technique gave a 100-fold improvement in the speed of analysis. The mosaic density in diabetics was significantly reduced relative to healthy subjects (P = 0.018), and mosaic density declined with progression of type 2 diabetes (ANOVA P = 0.036; Pearson P = 0.007).

Conclusions : A progressive degradation of the subbasal nerve plexus over a wide area is apparent in type 2 diabetes and this study establishes values for nerve density over a large area of the central cornea.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.