Remarkable improvements in optical coherence tomography (OCT) technology have resulted in highly sophisticated, noninvasive machines allowing detailed and advanced morphological evaluation of all retinal and choroidal layers. Postproduction semiautomated imaging analysis with dedicated public-domain software allows precise quantitative analysis of binarized OCT images. In this regard, the choroidal vascularity index (CVI) is emerging as a new imaging tool for the measurement and analysis of the choroidal vascular system by quantifying both luminal and stromal choroidal components. Numerous reports have been published so far regarding CVI and its potential applications in healthy eyes as well as in the evaluation and management of several chorioretinal diseases. Current literature suggests that CVI has a lesser variability and is influenced by fewer physiologic factors as compared to choroidal thickness. It can be considered a relatively stable parameter for evaluating the changes in the choroidal vasculature. In this review, the principles and the applications of this advanced imaging modality for studying and understanding the contributing role of choroid in retinal and optic nerve diseases are discussed. Potential advances that may allow the widespread adoption of this tool in the routine clinical practice are also presented.

Purpose: The purpose of this study was to compare the choriocapillaris plexus in eyes with intermediate AMD (iAMD), with or without neovascular AMD in the fellow eye, using optical coherence tomography angiography (OCTA). Methods: We collected data from 42 eyes with iAMD from 42 patients who had obtained OCTA. This cohort was divided into two subgroups according to the status of the fellow eye, yielding a group of 20 cases with bilateral intermediate AMD (bilateral iAMD group) and 22 cases with neovascular AMD in the fellow eye (unilateral iAMD group). An additional control group of 20 eyes from 20 healthy subjects was included for comparison. Main outcome measures were: (1) the percent of nondetectable perfused choriocapillaris area and (2) the average choriocapillaris signal void size. Results: No differences in the percent of nondetectable perfused choriocapillaris area were found among the three groups (2.3 ± 1.4% in the unilateral iAMD group, 1.5 ± 0.9% in the bilateral iAMD group, and 1.7 ± 1.4% in the control group, respectively). The average choriocapillaris signal void size, however, was significantly increased in unilateral iAMD eyes (293.7 ± 71.2 μm²) compared to both bilateral iAMD (241.5 ± 51.6 μm², P = 0.031) and control (212.7 ± 48.6 μm², P = 0.001) eyes. Conclusions: Intermediate AMD eyes of patients with neovascular AMD in the fellow eye have an increased average choriocapillaris signal void size compared to eyes without neovascular AMD in the fellow eye. If replicated in future studies, choriocapillaris signal void size may prove to be a useful parameter for evaluating eyes with AMD.

Imaging and histopathological studies have demonstrated that structural changes of the retina affect subjects with Alzheimer’s disease (AD) or mild cognitive impairment (MCI). The aim of this study was to quantitatively investigate the retinal vessels in these disorders, using dynamic vessel analyzer (DVA) and optical coherence tomography angiography (OCTA) analysis. Twelve subjects with AD, 12 subjects with MCI, and 32 gender- and age-matched controls were prospectively enrolled. Mean ± SD age was 72.9 ± 7.2 years in the AD group, 76.3 ± 6.9 years in the MCI group, and 71.6 ± 5.9 years in the control group (p = 0.104). In the DVA dynamic analysis, the arterial dilation was decreased in the AD group (0.77 ± 2.06%), in the comparison with the control group (3.53 ± 1.25%, p = 0.002). The reaction amplitude was decreased both in AD (0.21 ± 1.80%, <0.0001) and MCI (2.29 ± 1.81%, p = 0.048) subjects, compared with controls (3.86 ± 1.94%). OCTA variables did not differ among groups. In the Pearson correlation analysis, amyloid β level in the cerebrospinal fluid was directly correlated with the arterial dilation (R = 0.441, p = 0.040) and reaction amplitude (R = 0.580, p = 0.005). This study demonstrate that Alzheimer’s and MCI subjects are characterized by a significant impairment of the retinal neurovascular coupling. This impairment is inversely correlated with the level of amyloid β in the cerebrospinal fluid.