Associations of Retinal Vessel Geometry and Optical Coherence Tomography Angiography Metrics With Choroidal Metrics in Diabetic Retinopathy.

Purpose: To elucidate the mechanism underlying changes in choroidal metrics (choroidal thickness [CT], choroidal vascularity index [CVI], and choriocapillaris [CC] flow deficit [FD]) observed in diabetic retinopathy (DR) and examine the association of choroidal metrics with both retinal vessel geometry and optical coherence tomography angiography (OCTA) metrics. Methods: Overall, 133 eyes of 133 patients were analyzed retrospectively. Retinal vessel geometry parameters were assessed using semiautomated software. The OCTA metrics and CT were calculated using automated algorithms provided by the manufacturer, whereas the CVI and CC-FD were calculated using ImageJ software from the binarized choroid B-scan image and the CC slab provided by the manufacturer, respectively. To assess the associations among choroidal metrics, retinal vessel geometry, and OCTA metrics, multivariable regression analyses were performed while controlling for clinical features and DR severity. Results: In the multivariable linear regression analysis, CT (β = -399.84; P = 0.014) and CVI (β = -2.34; P = 0.021) showed significant associations with the arteriole-venule ratio, which is a ratio of central retinal arteriolar equivalent caliber with respect to central retinal venular equivalent caliber. The CC-FD showed a significant association with the fractal dimension of retinal arteriolar network (β = -2.90; P = 0.040). In contrast, the OCTA metrics showed no significant association with the choroidal metrics. Conclusions: The CT, CVI, and CC-FD in patients with DR were associated with retinal arteriolar geometry parameters rather than OCTA metrics, which indicates an association between choroidal changes and hemodynamic alterations in retinal arterioles and venules.