Morphologic alterations of both the stromal and subbasal nerves in the corneas of patients with diabetes

Purpose: To evaluate the subbasal and the stromal nerves of the corneas of patients with type 2 diabetes with in vivo confocal microscopy and to compare them with those of nondiabetic patients. Methods: Thirty-five corneas of patients with type 2 diabetes and 24 corneas of age-matched control subjects were included in the study. Patients with diabetes were further classified with respect to the stage of retinopathy. Subbasal and stromal nerve plexus morphology and thickness were evaluated with in vivo confocal microscopy. Subbasal long nerve fiber (LNF) and total nerve branch (NB) densities were calculated. Results: The mean stromal nerve thickness was significantly higher in patients with diabetes (8.99 +/- 2.32 mu m) than that of the control subjects (5.69 +/- 1.49 mu m; Mann-Whitney U test; P<0.001). The proportion of curved stromal nerves in patients with diabetes (45.7%) was also higher than that of normal subjects (20.8%; chi(2), P=0.05). Subbasal LNF and NB densities were found to significantly lower in the corneas of patients with diabetes (28.3 +/- 10.4 and 39.7 +/- 13.2 nerve/mm(2), respectively) than those of the control subjects (34.1 +/- 5.7 and 58.5 +/- 12.4 nerve/mm(2), respectively; Mann-Whitney, P=0.012 and P<0.001). In addition, the subbasal nerve plexus of patients with diabetes appeared significantly thicker and more tortuous than those of the control subjects (Mann-Whitney, P=0.002 and P=0.001). Conclusion: Both stromal and subbasal nerves appear abnormal in the corneas of patients with diabetes. Patients with proliferative diabetic retinopathy show more pronounced nerve alterations than patients who do not have diabetic retinopathy.