Longitudinal Changes in the Peripapillary Retinal Nerve Fiber Layer Thickness of Patients With Type 2 Diabetes.

IMPORTANCE

Type 2 diabetes is expected to accelerate age-related peripapillary retinal nerve fiber layer (pRNFL) loss, but limited information on the rate of reduction in pRNFL thicknesses in patients with type 2 diabetes is available.

OBJECTIVE

To investigate longitudinal changes in pRNFL thickness in patients with type 2 diabetes, with or without diabetic retinopathy (DR).

DESIGN, SETTING, AND PARTICIPANTS: A total of 164 eyes of 63 healthy individuals and 101 patients with type 2 diabetes (49 patients without DR [non-DR group] and 52 patients with mild to moderate nonproliferative DR [NPDR group]) were enrolled in this prospective, longitudinal, observational study from January 2, 2013, through February 27, 2015. Participants were followed up for 3 years, and the peripapillary mean and sector RNFL thicknesses were measured at 1-year intervals. The mean rate of pRNFL loss was estimated using a linear mixed model and compared among the 3 groups. Follow-up was completed on March 16, 2018, and data were analyzed from April 2 through July 27, 2018.

EXPOSURE

Type 2 diabetes.

MAIN OUTCOMES AND MEASURES

The rate of reduction in pRNFL thickness in patients with type 2 diabetes.

RESULTS

A total of 164 participants (88 women [53.7%]; mean [SD] age, 58.2 [8.7] years) were included in the study analysis. The mean (SD) age of the control group was 56.5 (9.3) years (39 women [61.9%]); the non-DR group, 59.1 (9.4) years (26 women [53.1%]); and the NPDR group, 59.4 (11.0) years (23 women [44.2%]). Mean (SD) duration of type 2 diabetes was 7.1 (4.4) years in the non-DR group and 13.2 (8.4) years in the NPDR group. The baseline mean (SD) pRNFL thickness was 96.2 (11.0) μm in the control group, 93.5 (6.4) μm in the non-DR group, and 90.4 (7.9) μm in the NPDR group. During 3 years of follow-up, these values decreased to 95.0 (9.2) μm in the control group, 90.3 (6.4) in the non-DR group, and 86.6 (7.9) μm in the NPDR group. In a linear mixed model, the estimated mean pRNFL loss was -0.92 μm/y in the non-DR group (P < .001) and -1.16 μm/y in the NPDR group (P < .001), which was 2.9-fold (95% CI, 1.1-14.8; P = .003) and 3.3-fold (95% CI, 1.4-18.0; P < .001) greater, respectively, than that of the control group (-0.35 μm/y; P = .01).

CONCLUSIONS AND RELEVANCE

Progressive reduction of pRNFL thickness was observed in healthy controls and patients with type 2 diabetes without and with DR; however, type 2 diabetes was associated with a greater loss of pRNFL regardless of whether DR was present. These findings suggest that pRNFL loss may occur in people with type 2 diabetes even in the absence of DR progression.