Diagnosis of neuropathy and risk factors for corneal nerve loss in type 1 and type 2 diabetes: A corneal confocal microscopy study
Methods: 490 participants including 72 healthy controls, 149 with type 1 diabetes and 269 with type 2 diabetes underwent detailed assessment of peripheral neuropathy and CCM in relation to risk factors.
Results: Corneal nerve fibre density (CNFD) (P<0.0001, P<0.0001), branch density (CNBD) (P<0.0001, P<0.0001) and length (CNFL) (P<0.0001, P=0.02) were significantly lower in patients with type 1 and type 2 diabetes, compared to controls. CNFD (P<0.0001), CNBD (P<0.0001) and CNFL (P<0.0001) were lower in type 1 diabetes compared to type 2 diabetes. Receiver operating characteristics (ROC) curve analysis for the diagnosis of DPN demonstrated a good area under the curve (AUC) for CNFD=0.81, CNBD=0.74 and CNFL=0.73. Multivariable regression analysis showed a significant association between reduced corneal nerve fibre length with age (β=-0.27, P=0.007), HbA1c (β=-1.1, P=0.01) and weight (β=-0.14, P=0.03) in patients with type 2 diabetes and with duration of diabetes (β=-0.13, P=0.02), LDL cholesterol (β=1.8, P=0.04), and triglycerides (β=-2.87, P=0.009) in patients with type 1 diabetes.Conclusion: CCM identifies more severe corneal nerve loss in patients with type 1 compared to type 2 diabetes and shows good diagnostic accuracy for DPN. Furthermore, the risk factors for a reduction in corneal nerve fibre length differ between type 1 and type 2 diabetes.