The nerve fiber bundle of the optic nerve is separated from the choroid by the border tissue of Jacoby. Regarding the role of the choroid in the blood supply to the optic nerve head, controversy persists as to whether the prelaminar region's arterial supply is derived primarily from the peripapillary choroid or the branches of the circle of Zinn-Haller, which is itself supplied by the short posterior ciliary arteries. Previously, Na et al. has shown using optical coher-ence tomography angiography (OCT-A) that the prelaminar region of the optic nerve head might be supplied by the peripapillary choroid in addition to the known major blood supply from the short posterior ciliary arteries.1 Further, OCT-A has revealed growing evidence that glaucoma is associated with decreased parapapillary choroidal microvasculature.2,3
Lower parapapillary choroidal vessel density (VD) with B-zone parapapillary atrophy (PPA) at baseline is associated with future visual field progression
This study by Park and colleagues is the first to demonstrate that lower parapapillary choroidal vessel density (VD) with B-zone parapapillary atrophy (PPA) at baseline is associated with future visual field progression in glaucoma. The clinical relevance of the study is that it is the first prospective one showing that patients with lower parapapillary choroidal VD at baseline need careful monitoring for future glaucoma progression.
There are some limitations to this study: (1) As only PPA(+) eyes were included, it is not clear whether the same results may be obtained for PPA(-) eyes or whether PPA itself may be a surrogate factor. Also, the boundary of PPA was delineated on the en face choroidal map of OCT-A, not on disc photography, which might have affected the determined size of PPA;4 (2) As seen in the figures, retinal blood vessels were included in the analysis of the choroidal VD; (3) Baseline IOP data were not provided or analyzed.
However, the current paper raised the promising possibility that OCT-A can be a useful tool to complement current structural and functional assessment in glaucoma. A future longitudinal follow-up study using OCT-A may further clarify the causal relationship between VD and optic nerve damage in glaucoma.