Automated Evaluation of Parapapillary Choroidal Microvasculature in Ischemic Optic Neuropathy and Open Angle Glaucoma.

Purpose: To determine whether parapapillary choroidal microvasculature (PPCMv) density as measured by optical coherence tomography angiography differs between nonarteritic anterior ischemic optic neuropathy (NAION) and primary open angle glaucoma (POAG). Methods: Thirty-seven eyes with chronic NAION, 34 unaffected fellow eyes with NAION, 47 moderate and severe POAG eyes, and 54 healthy control subjects were evaluated. Automated PPCMv density was calculated using custom Matlab software in inner and outer annuli around the optic nerve region in addition to peripapillary superficial retinal vessels. Results: Linear models showed no difference in peripapillary retinal nerve fiber layer between NAION and POAG eyes. Mean peripapillary superficial small vessels in the NAION and POAG groups were 36.62 ± 7.1% and 39.72 ± 8.18% without a statistically difference between them (P = 0.16). Mean inner and outer annular region PPCMv densities in the NAION group were 26.55 ± 9.2% and 17.81 ± 6.9%, which were not different from unaffected fellow eyes and the control group. However, the POAG group had significantly reduced PPCMv density in both inner and outer annuli with values of 15.84 ± 6.5% and 12.80 ± 5.0%, respectively, compared with normal subjects (both P < 0.001). Inner and outer circle PPCMv densities were also significantly reduced in the POAG group compared with the NAION group. Conclusions: Reduced PPCMv density in POAG eyes shows that deep optic nerve head ocular blood flow may contribute to axonal damage in patients with glaucoma.