Automated evaluation of parapapillary choroidal microvasculature in crowded optic discs: a controlled, optical coherence tomography angiography study

AIM: To compare superficial and deep vascular properties of optic discs between crowded discs and controls using optical coherence tomography angiography (OCT-A). METHODS: Thirty patients with crowded discs, and 47 control subjects were enrolled in the study. One eye of each individual was included and OCT-A scans of optic discs were obtained in a 4.5×4.5 mm2 rectangular area. Radial peripapillary capillary (RPC) density, peripapillary retinal nerve fiber layer (pRNFL) thickness, cup volume, rim area, disc area, cup-to-disc (c/d) area ratio, and vertical c/d ratio were obtained automatically using device software. Automated parapapillary choroidal microvasculature (PPCMv) density was calculated using MATLAB software. When the vertical c/d ratio of the optic disc was absent or small cup, it was considered as a crowded disc. RESULTS: The mean signal strength index of OCT-A images was similar between the crowded discs and control eyes (P=0.740). There was no difference in pRNFL between the two groups (P=0.102). There were no differences in RPC density in whole image (P=0.826) and peripapillary region (P=0.923), but inside disc RPC density was higher in crowded optic discs (P=0.003). The PPCMv density in the inner-hemisuperior region was also lower in crowded discs (P=0.026). The pRNFL thickness was positively correlated with peripapillary RPC density (r=0.498, P<0.001). The inside disc RPC density was negatively correlated with c/d area ratio (r=-0.341, P=0.002). CONCLUSION: The higher inside disc RPC density and lower inner-hemisuperior PPCMv density are found in eyes with crowded optic discs.