Macular microcirculation changes in incident type 2 diabetes without fundus Photography-Detectable diabetic Retinopathy: A 6-Year nested Case-Control study

AIMS: To investigate 6-year macular microcirculation changes in participants who developed incident type 2 diabetes mellitus (T2DM) during follow-up but had no fundus photography-detectable diabetic retinopathy (DR), and to identify factors associated with early microvascular abnormalities. METHODS: This nested case-control study compared participants with incident T2DM without DR with age-matched controls without diabetes. All participants underwent ophthalmic examinations and 6 x 6 mm macular optical coherence tomography angiography at both visits. Vessel density (VD) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP), foveal avascular zone-related parameters, and foveal density 300 were analyzed using generalized estimating equations. RESULTS: Sixty-eight eyes from 40 participants with incident T2DM and 204 control eyes were included. Both groups showed decreases in SCP and DCP VD over 6 years. Reductions in DCP VD were greater in T2DM eyes than in controls (all P < 0.05). Microvascular abnormalities developed in 23 diabetic eyes and were independently associated with longer diabetes duration. CONCLUSION: Incident T2DM eyes showed greater decline in DCP VD than controls without fundus photography-detectable DR. These findings highlight the importance of early longitudinal monitoring of retinal perfusion in T2DM.