Longitudinal Neural and Microvascular Changes in Type 2 Diabetic Patients Without Retinopathy: A 2-Year Prospective Cohort Study.

PURPOSE: To compare the 2-year longitudinal changes in macular ganglion cell-inner plexiform layer thickness (GCIPLT) and superficial capillary plexus (SCP) vessel density between patients with type 2 diabetes mellitus (T2DM) without retinopathy (non-DR) and healthy controls.

DESIGN

Prospective observational cohort study.

METHODS

T2DM patients without clinical retinopathy at baseline and after a 2-year follow-up, along with age- and sex-matched healthy controls, were recruited from the community in Guangzhou, China. Measurements of macular GCIPLT, retinal thickness (RT), and SCP vessel density were conducted at baseline and at the 2-year follow-up. Linear mixed-effects models were used to estimate absolute and relative rates of changes and to compare absolute rates between the 2 groups.

RESULTS

A total of 282 eyes (141 in the control group and 141 in the non-DR group) were included in the analysis. Significant reductions in GCIPLT and GCIPLT/RT occurred only in the non-DR group, with GCIPLT decreasing by -0.229 µm/y (95% CI = -0.313 to -0.144; P < .001) and 0.324 % (95% CI = 0.444 to 0.204; P < .001), approximately 5-fold faster than in the control group. After adjusting for confounding factors, the longitudinal rates of RT, GCIPLT, and GCIPLT/RT were significantly accelerated in the non-DR group compared to the control group by -0.603 µm/y (95% CI = -0.939 to -0.268; P < .001), -0.189 µm/y (95% CI = -0.306 to -0.073; P = .001), and -0.073 % (95% CI = -0.118 to -0.028; P = .001), respectively. Although longitudinal changes in SCP vessel density did not show significant differences between the 2 groups (P = .861).

CONCLUSIONS

Our findings suggest that neurodegenerative changes may precede microvascular alterations in non-DR patients, indicating that monitoring of GCIPLT is crucial for patients with long-standing diabetes, even in the absence of retinopathy.