Fig 3. Segmental valuation of the peripapillary vessel density.

The optic nerve was indicated as a circle, and the outer margin was set at 750 μm from this circle margin. The donut-shaped portion between the outer margin and the optic nerve margin was divided into four segments, namely the superotemporal, inferotemporal, superonasal, and inferonasal segments (A); each segment was extracted as a region of interest (ROI) (B); large vessels were detected and deleted (C); and finally, the binary ROI of the peripapillary vessels, with large vessels excluded, was retained (D). ON, optic nerve; ST, superotemporal; IT, inferotemporal; SN, superonasal; IN, inferonasal.