Corneal nerve fiber pathology in Japanese type 1 diabetic patients and its correlation with antecedent glycemic control and blood pressure

Aims/Introduction: Morphological changes to corneal C‐fibers in Japanese type 1 diabetic patients were visualized by corneal confocal microscopy (CCM). The effects of prior glycemic control and blood pressure on morphological parameters were clarified. Materials and Methods: Corneal nerve fibers were visualized by CCM in 38 Japanese type 1 diabetic patients (14 with and 24 without neuropathy) and 38 controls. Morphological parameters were compared and related to annual mean HbA1c, blood pressure, and serum lipid levels of previous years prior to CCM examination. Results: Compared with controls, diabetic patients had reduced corneal nerve fiber length (CNFL; 9.80 ± 0.38 vs 13.65 ± 0.88 mm/mm²; P < 0.001), reduced density (CNFD; 25.32 ± 1.04 vs 36.62 ± 2.37/mm²; P < 0.0005), lower frequency of beading (22.38 ± 0.73 vs 30.44 ± 1.03/0.1 mm; P < 0.0001), and increased tortuosity (3.13 ± 0.09 vs 1.74 ± 0.06; P < 0.0001). These changes were found in patients without neuropathy. There was no difference in nerve branches between controls and diabetic patients. The mean annual HbA1c level for the 7–10 years prior to CCM examination was an independent predictor of reduced CNFL and CNFD; HbA1c levels obtained 1–3 months and 1 year prior to CCM, as well as blood pressure 3, 5, and 6 years prior to CCM, were independent predictors of reduced beading frequency. Conclusions: Corneal confocal microscopy is a novel, noninvasive technique to evaluate morphological changes of corneal C‐fibers in type 1 diabetes. Antecedent hyperglycemia and blood pressure have different time‐dependent effects on CNFL and CNFD and the frequency of beading. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00157.x, 2011)