What is the relationship between the choroidal vascularity ındex (CVI) and myopia?

Purpose To examine the detailed vascular and morphological characteristics of the choroidal tissue in subjects with myopia. Methods A total of 111 subjects with myopia were included in the study. The study was conducted in three groups according to spherical equivalent(SE). Group 1 comprised subjects with low myopia (SE between 0.00 diopter (D) and - 3.00 D), Group 2 included those with moderate myopia (SE between - 3.25 D and - 6.00 D), and Group 3 consisted of subjects with high myopia (SE of - 6.25 D or worse). The following parameters were measured: axial length(AL), SE, central macular thickness (CMT), choroidal thickness(CT), total choroidal area(TCA), luminal area(LA), stromal area(SA), LA/SA ratio, and choroidal vascularity index(CVI). The binarization method was employed to calculate the TCA, LA, SA, LA/SA ratio, and CVI values. A comparison was conducted between the groups with respect to all parameters. Results In patients with high myopia, CT values (subfoveal, nasal, and temporal) were significantly thinner than moderate and low myopic patients (< 0.001). The low myopic group exhibited significantly elevated LA, SA, and TCA values in comparison to the moderate and high myopic groups. Conversely, the LA/SA ratio and CVI values were observed to be higher in patients with high myopia than in those with low or moderate myopia. A statistically significant negative correlation was identified between CVI and LA/SA values and SE(r = - 0.270, P = 0.004; r = - 0.291, P = 0.002, respectively). A statistically significant positive correlation was identified between CVI and LA/SA values and AL (r = 0.269, P = 0.004; r = 0.281, P = 0.003, respectively). Conclusion In young adults, high myopia has been linked to significant choroidal thinning in the macular region. This reduction in choroidal thickness is largely attributed to a decrease in the stromal component of the choroid, rather than the luminal (vascular) component. Trial registration date and number 08/06/2022, 2022-49.