Acute hyperglycemia compromises the responses of choroidal vessels using swept-source optical coherence tomography during dark and light adaptations

Abstract

PurposeTo clarify the effects of acute hyperglycemia on the responses of choroidal structural components and vascularity index during light modulation in healthy participants using techniques including image binarization and artificial intelligence (AI) segmentation based on swept-source optical coherence tomography (SS-OCT).MethodsTwenty-four eyes of 24 healthy participants were imaged at different stages after ambient light, 40 min of dark adaptation, and 5 min of light adaptation in two imaging sessions: control and after receiving 75 g of oral glucose solution. The choroidal structural parameters, including luminal volume (LV), stromal volume (SV), total choroidal volume (TCV), and choroidal vascularity index (CVI) within a 6 mm area were determined using a custom algorithm based on image binarization and AI segmentation of SS-OCT. These measurements were compared among the conditions after adjusting for axial length, age to identify the differences.ResultsIn the dark, CVI decreased (-0.36 ± 0.09%) significantly in acute hyperglycemia compared to the control condition. During the transition to ambient light, there was an increasing trend in the choroidal parameters compared with the control experiment. However, only TCV (0.38 ± 0.17 mm3) and LV (0.27 ± 0.10 mm3) showed a significant increase at the time point of 5 min after ambient light.ConclusionAnalysis of choroidal structural parameters and CVI based on SS-OCT images is a potentially powerful method to objectively reflect subtle changes in neurovascular coupling between the choroid and photoreceptor during dark adaptation.

Impact of Brightness on Choroidal Vascularity Index

“…The CVI is calculated as a ratio between the LCA and TCA [2]. Since its introduction, the CVI has been widely used in international research, but recently some concerns have been raised about its reliability, due to the possible influence of the image brightness at acquisition time on its evaluation [11,14,23,25,27] or the influence of dark-or light-adapted eyes and hyperglycemia on the resulting CVI [38]. Although OCT-angiography (OCTA) allows us to study in vivo retinal and choroidal vascularization, similar limitations due to signal attenuation are present even in OCT-angiography (OCTA), as denoted by Di Pippo et al in their comparison between EDI-OCT and OCTA for evaluating AMD [39].…”