Effects of prolonged type 2 diabetes on changes in peripapillary retinal nerve fiber layer thickness in diabetic eyes without clinical diabetic retinopathy

To identify the effects of prolonged type 2 diabetes (T2DM) on changes in peripapillary retinal nerve fiber layer (pRNFL) thickness in patients without clinical diabetic retinopathy. Subjects were divided into two groups: controls and patients with T2DM (DM group). After the initial visits, the pRNFL thicknesses were measured three more times at 1-year intervals. Subgroup analyses were performed in patients with T2DM duration >= 10 years. The mean pRNFL thickness at each visit was 95.8 +/- 8.1, 95.4 +/- 8.3, 94.9 +/- 8.1, and 94.5 +/- 8.3 mu m in the control group (P=0.138) (n=55); and 93.4 +/- 9.1, 92.1 +/- 9.3, 90.9 +/- 9.3, and 89.5 +/- 9.2 mu m in the DM group (P<0.001) (n=85). The estimated rate of reduction in mean pRNFL thickness was -0.45 <mu>m/year in the control group and -1.34 mu m/year in the DM group, respectively. In the DM group, the BCVA and HbA1c (both P=0.001) were significant factors associated with pRNFL reduction. In patients with T2DM duration >= 10 years, the estimated pRNFL reduction rate was -1.61 mu m/year, and hypertension was a significant factor affecting the pRNFL reduction (P=0.046). We confirmed rapid pRNFL reduction over time in T2DM, and the reduction rate was higher in patients with T2DM >= 10 years. Additionally, BCVA and HbA1c levels were significantly associated with the change in pRNFL thickness in T2DM patients.