Measurement and analysis of choroidal vascularity index and subfoveal choroidal thickness in central serous chorioretinopathy

Abstract

Objective To observe the choroidal vascularity index (CVI) and the subfoveal choroidal thickness (SFCT) of central serous chorioretinopathy (CSC), and to compare the stability and consistency of the two methods of measurement. Methods A retrospective study. Thirty-one patients with unilateral acute CSC who visited the Department of Ophthalmology of Beijing Friendship Hospital for the first time during the period from Nov 1st, 2016 to Mar 18th, 2018 were included in the study. Thirty-one healthy age-matched subjects were enrolled as controls. All CSC affected eyes and their fellow eyes and healthy eyes were scanned by single-line enhanced depth imaging of OCT through central fovea of macula to measure their SFCT. The image was binarized and then the CVI of a 1500 μm range below fovea was calculated, i.e. the ratio of vascular (or lumen) area to total choroidal area. CVI and SFCT were compared among CSC eyes, fellow eyes and healthy eyes by variance analysis. Intra-group correlation coefficient (ICC), Bland-Altman curve and coefficient of variation (CV) were used to analyze the repeatability, consistency and stability of CVI and SFCT; and Medcalc18.2.1 software was used to draw the Bland-Altman curve and observe the consistency of the two measurement methods. Results There were statistically significant differences in CVI and SFCT between CSC affected eyes and fellow eyes (t=3.470, 2.844; P=0.001, 0.006), CSC affected eyes and healthy eyes (t=6.977, 6.277; P<0.001,<0.001), fellow eyes and healthy eyes (t=3.508, 3.433; P=0.001, 0.001). Relative consistency analysis of CVI and SFCT showed that the ICC of single measurement and average measurement of CVI were 0.967 and 0.983 respectively, and that of single measurement and average measurement of SFCT were 0.937 and 0.967 respectively. The consistency of CVI and of SFCT was very good. The ICC value of CVI was slightly higher than that of SFCT. The results of repeatability analysis of CVI and SFCT showed that the difference between the two CVI measurements was smaller, and the difference between the two SFCT measurements was larger. And CVI and SFCT stability analysis results showed that the CV of CVI and SFCT were 10.5% and 25.3% respectively. CVI has smaller CV than SFCT. Conclusions Compared with healthy eyes, CVI and SFCT are increased in CSC affected eyes and fellow eyes. And compared with SFCT, CVI has better consistency, repeatability and stability. Key words: Central serous chorioretinopathy; Tomography, optical coherence; Choroidal vascularity index; Subfoveal choroidal thickness