Abstract
Purpose :
Choroidal vascularity index (CVI) is becoming an important marker for choroidal changes in both healthy and diseased eyes. There is currently no standardized method for computing CVI, and one potential issue affecting CVI is the definition of the minimum intensity of the pixels (indicating the vascular areas) in B-scans. In this study, we investigated whether defining the minimum intensity of the pixels by two different methods significantly affects the estimated CVI values.
Methods :
We analysed 38 B-scans acquired from the right eye of children aged 8-16 years using the Zeiss Cirrus 5000 with enhanced depth imaging mode. Horizontal B-scans of 9 mm (1055-pixel) width and pixel aspect ratio of 0.33 were exported from the Cirrus in Tiff format. All image processing was performed in Fiji /ImageJ2 (ver. 2.14/1.54f). B-scans were cropped to measure CVI in the central 6 mm (3 mm in each side of the fovea). After manual segmentation of the choroid, the minimum pixel intensity was determined by two methods: minimum intensity of the all-choroid area (method-1) and mean value of lowest intensity of 3 regions with a 9-pixel diameter defined in the Haller’s layer (method-2).
Results :
The mean CVI obtained with method-1 was 69.0% (SD=2.5) and with method-2 was 70.0% (SD= 2.2). A Bland-Altman analysis showed that CVI obtained by method-2 had a significantly higher CVI, with a mean difference of 1% (P<0.001) and the 95% limits of agreement ranged from 1.2% to − 3.2%. There was a statistically significant negative correlation between CVI computed with method-1 and age (p=0.02).
Conclusions :
Our results show that the method used to define the intensity of the vascular area in B-scans can lead to significant changes in CVI. Further work is necessary to determine which method is more accurate.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.