Abstract
Purpose: :
To image corneal nerves in diabetes patients with and without retinopathy using in vivo confocal microscopy, and correlate with corneal sensation and vibration perception threshold (VPT).
Methods: :
The corneal subbasal nerve plexus was examined with the cornea module of the Heidelberg Retina Tomograph II in 24 normal subjects and 68 patients with diabetes mellitus (DM) with and without retinopathy (19% DM type I; 81% DM Type II). Scans obtained were analyzed by a masked observer according to number, density, branching and tortuosity of corneal nerves using standardized pictures and Image-J-software. Cochet-Bonnet esthesiometry was used to measure corneal sensitivity. In addition, VPT was tested in the area of the thenar and the malleolus of the ankle. Statistics were performed using non-parametric tests.
Results: :
The mean age of the study cohort was 58 years (25-81 years). 26% of the patients showed a nonproliferative retinopathy (NPDR), 37% of patients suffered from proliferative retinopathy (PDR). A significant difference was present between normal subjects and diabetes patients concerning number, density, and branching (all p <= 0.001) of corneal nerves, corneal sensitivity (p = 0.02) and VPT at the thenar and malleolus (both p < 0.001). No significant difference existed between diabetes patients without retinopathy, NPDR and PDR, and between patients with DM type I and II. There was no correlation of corneal parameters with age in diabetes patients and controls. Corneal sensitivity significantly correlated with number, branching (both p </= 0.003) and density (p = 0.02) of corneal nerves. VPT at the malleolus corresponded well with the number of corneal nerves (p = 0.03). Diabetes patients with normal corneal sensation and VPT showed a decreased number, density, and branching of corneal nerves compared to normal subjects (all p </= 0.005).
Conclusions: :
Diabetes patients show a decrease in corneal sensitivity and vibration sensation as well as a reduction in corneal innervation independent of diabetes type and stage of diabetic retinopathy. In vivo confocal microscopy of corneal nerves is more sensitive than estesiometry and vibration perception testing to identify early diabetic neuropathy.
Keywords: imaging/image analysis: clinical • cornea: clinical science • diabetes