Evaluation of choroidal and retinal characteristics using oct and octa in posterior pole-dominant and peripheral retina-dominant diabetic retinopathy (dr)

Aim: Diabetic retinopathy (DR), regardless of the severity of the retinopathy, may in some cases begin in the posterior pole and impair vision at a very early stage even when there are almost no signs in the peripheral retina. In other cases, the disease may progress to an advanced or even proliferative stage in the peripheral retina without affecting the posterior pole at all, resulting in delayed diagnosis and treatment since vision is only affected in the later stages. In this study, we aimed to investigate whether these two distinct presentations of the disease are associated with differences in retino-choroidal vascular characteristics, particularly focusing on the choroidal vasculature. Materials and Methods: Cases were classified according to their clinical presentation as "Posterior Pole Dominant (PPD)" and "Peripheral Retina Dominant (PRD)" diabetic retinopathy (DR). A total of 70 eyes from 65 patients diagnosed with type 2 diabetes mellitus and DR were included, with 35 eyes categorized as PRD-DR and 35 as PPD-DR. All cases underwent 6×6 mm OCTA and macular OCT imaging using the Topcon DRI Triton Plus (Swept Source OCT) device. In the OCTA analysis, vascular densities of the retinal, retinochoroidal, and choroidal segments—specifically in the foveal and parafoveal subsegments—were evaluated and compared both within and between groups. Results: In PPD-DR cases, parafoveal vascular density was found to be lower compared to PRD-DR cases, with a higher degree of subsegmental variation, which was attributed to ischemic areas. In PPD-DR cases, nasal parafoveal subsegment vascular densities were preserved, whereas temporal and inferior parafoveal subsegment densities were decreased. A significant negative correlation was observed between choroidal foveal vascular density and retinal foveal vascular density, suggesting that healthy choroidal perfusion may have a protective effect against ischemia in the foveal region. This highlights the critical role of choroidal blood flow in the clinical presentation of diabetic retinopathy. Additionally, the positive correlation found between the retinal parafoveal region and the choroidal parafoveal and foveal vascular densities suggests that intact choroidal perfusion in both the foveal and parafoveal regions plays a key role in macular perfusion and the prevention of macular ischemia. Conclusion: Choroidal blood flow plays a vital and decisive role in the clinical course of diabetic retinopathy. Therefore, the evaluation of choroidal circulation should be included in the diagnosis and treatment of DR patients. Keywords: Diabetic retinopathy, SS-OCTA, Choroid