Abstract
Purpose:
Non-invasive and repeated imaging of the corneal sub-basal nerve plexus is made possible by in vivo corneal confocal microscopy (CCM). This diagnostic technique can be used to monitor the status of neuropathy in diabetes patients because the corneal nerve plexus decreases with the progression of diabetic neuropathy. However, it is unclear which part of the sub-basal nerve plexus around the central cornea is captured by CCM, which may induce measurement errors when data are compared between patients or over time in the same patient. There is a whorl-like characteristic pattern of corneal sub-basal nerve plexus in the infero-central cornea and we examined the CCM images of the whorl-like patterns in patients with diabetes.
Methods:
A total of 19 diabetes patients and 7 healthy control subjects were examined by CCM to compare the characteristics of the corneal sub-basal nerve plexus around the center of the cornea (conventional method) and the whorl-like pattern in the infero-central cornea (study method) by using a Rostock Corneal Module/Heidelberg Retina Tomograph Ⅲ. The five clearest images of the sub-basal nerve plexus around the central cornea and the best image of the whorl-like nerve plexus in the infero-central cornea were selected for further analysis. Nerve analysis was carried out using Neuron J to measure the total corneal nerve fiber and branch length (CNFL) in addition to corneal nerve fiber and branch density (CNFD).
Results:
Total CNFL were significantly shorter in the DM group compared to the control group in both conventional and whorl-like methods (p = 0.0039 vs. p = 0.0047). We confirmed a significant decreasing trend of total CNFL with the progression of diabetes retinopathy, nephropathy, neuropathy, and the loss of corneal sensation. There was also significant correlation between conventional CNFL and whorl-like CNFL (r = 0.790, p < 0.0001). CNFL measured by the whorl-like method were significantly longer than that measured in conventional CNFL in healthy subjects and diabetes patients.
Conclusions:
As the whorl-like pattern is a characteristic structure of the infero-central cornea and whorl-like CNFL has the same decreasing trend as conventional CNFL, measurements of the whorl-like patterns in the corneal sub-basal nerve plexus would be more suitable for monitoring diabetic peripheral neuropathy compared with measurements by the conventional method.