Choroidal structural alterations in patients with type 2 diabetes mellitus without clinical diabetic retinopathy using ultra-widefield swept-source OCTA: A cross-sectional study

OBJECTIVE: This study aimed to quantitatively examine choroidal structural alterations in patients with type 2 diabetes mellitus (T2DM) of varying disease duration who did not present with clinical diabetic retinopathy (DR), using ultra-widefield swept-source optical coherence tomography angiography (UWF-SS-OCTA). METHODS: This cross-sectional study included 200 patients with T2DM without DR (200 eyes) and 78 healthy individuals (78 eyes). Based on diabetes duration, patients were categorized into three groups: 10 years (DM3, n = 60). UWF-SS-OCTA was used to quantify choroidal thickness (CT), choroidal vascular volume (CVV), and choroidal vascularity index (CVI) in the peripapillary region, the macula-centered UWF central area (1-12 mm), and the peripheral area (12-21 mm). One-way analysis of variance with post hoc testing assessed intergroup differences. Multivariable linear regression was performed to evaluate the associations between diabetes duration and choroidal parameters. RESULTS: Relative to healthy controls, patients in the DM3 group exhibited significant reductions in CT and CVV in all evaluated regions, along with decreases in CVI in most regions (all p < 0.05). When diabetic subgroups were compared, the DM3 group demonstrated significantly lower CT and CVV across all regions compared with the DM1 and DM2 groups (all p < 0.05). Central CVI showed a progressive decline with longer diabetes duration, while peripheral CVI differed significantly only between the DM3 and DM1 groups. Except for peripheral CVI, CT, CVV, and central CVI across all assessed regions were independently and negatively associated with diabetes duration (all p < 0.05). CONCLUSION: Patients with T2DM without DR demonstrated early choroidal thinning and vascular deterioration, which progressively worsened with longer diabetes duration. UWF-SS-OCTA revealed that the choroidal alterations in T2DM without DR were widespread but most pronounced in the peripheral regions, highlighting the importance of wide-field imaging for comprehensive assessment.