Evaluation of retinal vascular changes caused by type 2 diabetes mellitus depending on years by optical coherens tomography angiography

The primary objective of this study is to assess the early-stage impact of diabetes on retinal vascularity by juxtaposing OCTA (Optical Coherence Tomography Angiography) images of recently diagnosed, non-Diabetic Retinopathy (DR) individuals against a healthy cohort. Additionally, our investigation aims to probe the temporal effects of diabetes on vascular dynamics by scrutinizing OCTA images across varying durations of diabetes diagnosis devoid of DR indicators. This study comprised 29 eyes of 29 newly diagnosed diabetes mellitus patients without diabetic retinopathy (Group 1), 42 eyes of 42 patients diagnosed with diabetes mellitus within a maximum duration of 5 years (Group 2), and 27 eyes of 27 patients diagnosed with diabetes mellitus for durations between 5 and 10 years (Group 3). The subjects were recruited from the Department of Ophthalmology at Mersin University Faculty of Medicine Hospital between January 1, 2022, and May 1, 2022. Additionally, a control cohort of 35 eyes from 35 individuals, matched for age and gender distribution, was incorporated. Data acquired from Zeiss Cirrus 6000 Angioplex device-derived OCTA images using the 6x6 mm macular protocol were meticulously documented. The findings indicate that, despite the absence of clinically evident DR, diabetes progressively enlarged the Foveal Avascular Zone (FAZ) area post- initial diagnosis and reduced Vessel Density (VD) and Perfusion Density (PD) parameters within the central region. Notably, the diabetic cohort displayed diminished VD and PD parameters in the parafoveal inferior area and the perifoveal superior and inferior areas compared to the control group. Furthermore, Group 2 patients exhibited reduced VD across all parafoveal quadrants and decreased perifoveal superior and inferior VD parameters when contrasted with the control cohort. Patients in Group 3 showcased diminished perifoveal superior VD and parafoveal nasal VD compared to both newly diagnosed individuals and the control group. However, no statistically significant differences in any OCTA parameter were observed between the newly diagnosed patient group and the control cohort. In conclusion, this study underscores the detectable alterations in vascular parameters using OCTA even in the early stages without clinically manifested DR in diabetic patients. Keywords: Diabetic retinopathy, Vascular density, Retinal vascular disease, Optical coherence tomography angiography