Peripapillary choroidal vascularity index and microstructure of parapapillary atrophy

Abstract

PURPOSE. To investigate the association between the microstructure of b-zone parapapillary atrophy (bPPA) and choroidal vascularity index (CVI) determined by spectral-domain optical coherence tomography (SD-OCT) in glaucomatous eyes. METHODS. A total of 160 eyes of 160 primary open-angle glaucoma patients with bPPA were included. Total choroidal area (TCA), luminal area (LA), and CVI were measured at a 3.5-mm distance from the Bruch's membrane (BM) opening center by image binarization of SD-OCT B-scans. The widths of bPPA with BM (bPPA+BM) and without BM (bPPA-BM), and juxtapapillary choroidal thickness (JPCT) were measured on six radial SD-OCT images. OCT angiography-derived parapapillary deep-layer microvasculature dropout (MvD_P) was also derived. RESULTS. In the multivariate regression analysis, larger bPPA+BM was significantly associated with smaller TCA and smaller LA (P < 0.05, respectively), but not with CVI and JPCT (P > 0.05, respectively). Meanwhile, bPPA-BM was not significantly associated with TCA, LA, CVI, or JPCT in the multivariate regression analysis (P > 0.05). CONCLUSIONS. Despite significant relationship between the choroidal thinning and larger bPPA+BM, choroidal vascularity was not associated with the bPPA+BM width. These findings suggest that the presumed common pathogenic mechanism between RPE atrophy and peripapillary choroidal thinning may not be mediated by the impaired choroidal perfusion in glaucomatous eyes. Future studies on the mechanisms in explaining the relationship between the atrophy of retinal pigment epithelium (RPE) and choroid in glaucoma are needed.