Chorioretinal microvascular changes in patients with type 1 diabetes mellitus in the absence of diabetic retinopathy - an OCTA study

Abstract

Introduction. Diabetic retinopathy (DR) is the leading cause of visual impairment in the working-age population. Microvascular changes in the retina occur before clinical signs of DR appear. Optical coherence tomography angiography (OCTA) enables non-invasive visualisation of retinal microvasculature. The aim is to investigate retinal microvascular changes using OCTA in patients with type 1 diabetes mellitus (T1DM) without clinical DR.Methods. Cross-sectional study of 98 eyes from 49 subjects (29 T1DM patients, 20 healthy controls). All underwent comprehensive ophthalmic examination and OCTA (Cirrus 6000, 3×3 mm angiogram). Superficial capillary density (SCD, mm/mm²), perfusion density (PD, %), foveal avascular zone area (FAZ, mm²), central macular thickness (CMT) and macular volume were analysed. Demographic and clinical data were collected.Results. T1DM patients had significantly higher perfusion density (PD full right: median 38.20% vs. 37.40%, p=0.029). No significant differences were found for other OCTA parameters. FAZ showed a borderline increase in patients with comorbidities (p=0.055). No correlation was observed between OCTA parameters and diabetes duration or HbA1c levels. A positive correlation was found between total daily insulin dose and central macular vascular density. OCTA successfully demonstrated changes in the foveal microvascular zone that are not visible on clinical examination, while all other OCT and OCTA parameters showed no statistically significant difference between groups.Conclusion. OCTA can detect early microvascular changes in T1DM patients before clinical DR. Comorbidities and glycaemic control may influence OCTA parameters. Longitudinal studies are needed to assess predictive value for DR progression.