Abnormal Glycaemic Fluctuations Associated With Early Microvascular Changes in the Retina and Choroid of Nondiabetic Adults

AIMS: To evaluate the association between continuous glucose monitoring (CGM)-derived glycaemic variability indicators and early microvascular changes of the retina and choroid in nondiabetic individuals. MATERIALS AND METHODS: Community-based individuals at high risk for type 2 diabetes (T2DM) underwent detailed assessments including oral glucose tolerance tests (OGTT), CGM and ophthalmic imaging including optical coherence tomography angiography (OCTA). Based on the mean amplitude of glycaemic excursions (MAGE), 338 OGTT-confirmed nondiabetic participants were categorized as having normal glucose fluctuation (NGF) or abnormal glucose fluctuation (AGF). Between-group differences in foveal avascular zone (FAZ), blood flow density and thickness in retina and choroid were analysed. Multiple linear regression analysis was used to analyse the correlation between CGM metrics and blood flow density in retina and choroid. RESULTS: Compared with the NGF group (265 eyes from 265 participants), the AGF group (73 eyes from 73 participants) showed lower retinal blood flow density in the central (p = 0.007) and parafoveal temporal (p = 0.003) regions of the superficial layer and in the parafoveal temporal (p = 0.014) and parafoveal superior (p = 0.005) regions of the deep layer. In the choroid, the volume area ratio of large vessels (CVV/a) was reduced, whereas the choroidal vascular index (CVI) was increased in the AGF group. Choroidal thickness was decreased among individuals with AGF. CGM metrics such as MAGE and coefficient of variation (CV) were negatively correlated with the retinal and choroidal blood flow density. CONCLUSIONS: Increased glycaemic variability even in nondiabetic adults is associated with reduced blood flow density and decreased choroidal thickness. TRIAL REGISTRATION: ClinicalTrials.gov NCT03811470.