The Choroidal Vascularity Index Versus Optical Coherence Tomography Angiography in the Evaluation of the Choroid with a Focus on Age-Related Macular Degeneration

Abstract

The choroid is the most vascularized structure of the eye and it is fundamental for the trophism of the outer retina. Its proper functioning and homeostasis represent key points in maintaining normal retinal physiology. Choroidal alterations may be implicated in the development and progression of numerous pathologies; therefore, in-depth studies using imaging techniques can be of crucial relevance to understanding the pathophysiology of retinal-choroidal diseases. The advent of spectral-domain optical coherence tomography (SDOCT) has enabled the non-invasive study of the choroid in vivo and the most recent development, optical coherence tomography angiography (OCTA), allows for the high-resolution visualization of the choriocapillaris and the choroid in regard to vascularization. The choroidal vascularity index (CVI) is a new parameter calculated on SDOCT scans and is defined as the ratio of the luminal area to the total choroidal area. In this review, a study of the choroid using OCTA and CVI will be evaluated in depth and the pros and cons of these two methods will be analyzed, with a particular focus on age-related macular degeneration.

Impact of Brightness on Choroidal Vascularity Index

“…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].…”

“…Different brightnesses of OCT images, as well as different and operator-dependent tracking modes could explain the CVI values' ambiguity. The aforementioned differences represent the limitations of this method for evaluating choroidal vascularization, which has been validated and used in many manuscripts in the most recent literature [2,15,27,35,36,39,[46][47][48][49][50][51][52][53].…”

An Update on Multimodal Ophthalmological Imaging of Diffuse Choroidal Hemangioma in Sturge–Weber Syndrome

“…This technology enables the segmentation of choroid-retinal vascularization into distinct layers, including the superficial capillary plexus (SCP) and the deep capillary plexuses (DCP), the outer retina, and the choriocapillaris (CC). Figure 4 shows the OCTA segmentation into SCP, DCP, and CC layers [ 68 , 69 ].…”

“…This technology enables the segmentation of choroid-retinal vascularization into distinct layers, including the superficial capillary plexus (SCP) and the deep capillary plexuses (DCP), the outer retina, and the choriocapillaris (CC). Figure 4 shows the OCTA segmentation into SCP, DCP, and CC layers [68,69]. A recent study examined the role of OCTA in evaluating CCHs, underlying how it can provide insight into lesion characteristics by analyzing density, flow, and vascular patterns.…”

Evaluation of Choroidal Structure in Type 1 Macular Neovascularization Using Different Optical Coherence Tomography Analyses: Scale Bar and Binarization

“…Several researchers have analyzed the choroidal thickness in each layer using a scale bar in the OCT systems [ 7 , 8 , 9 ]. Recently, ratios of the luminal to the choroidal area (LC ratios, also known as choroidal vascularity index) based on binarized images have been proposed, and several studies have used this binarization method [ 10 , 11 , 12 , 13 , 14 ]. However, few studies have compared these OCT evaluations.…”