Differential reduction in corneal nerve fiber length in patients with type 1 or type 2 diabetes mellitus

Aim: To examine the relationship between corneal nerve fiber length (CNFL) and diabetic neuropathy (DN) status in patients with type I or type 2 diabetes mellitus (DM). Methods: In this cross-sectional study, we examined 25 diabetic patients without DN, 10 patients with mild ON, 8 patients with severe ON, and 9 controls without diabetes. ON status was assigned based on a combination of clinical symptoms, signs, and electrophysiological testing. Patients underwent corneal confocal microscopy (CCM) of the sub-basal nerve plexus. Post-hoc analysis of the CCM images was performed to quantify the average CNFL, and ANOVA was used to assess for differences in CNFL Results: All 25 subjects without DN had type 1 DM, and subjects with ON had type 2 DM. Participants with severe DN had significantly lower CNFL (12.5 +/- 6.1 mm/mm(2)) compared to controls (20.7 +/- 2.2 mm/mm(2)) (p = 0.009). However, lower CNFL was also found in participants with type 1 DM who did not have DN (15.1 +/- 4.7 mm/mm(2)) relative to controls (p = 0.033). Conclusions: CCM of the sub-basal nerve plexus may be an indicator of early peripheral nerve degeneration in type 1 DM. Type of diabetes, in addition to degree of neuropathy, may influence the extent of corneal nerve damage. (c) 2014 Elsevier Inc. All rights reserved.