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.