Comparison of peripapillary vessel density between preperimetric and perimetric glaucoma evaluated by OCT-angiography

PURPOSE: To determine peripapillary vessel density in eyes with perimetric glaucoma (PG) or preperimetric glaucoma (PPG) compared to normal controls using optical coherence tomography-angiography (OCT-A). METHODS: We recruited 13 patients with unilateral perimetric normal-tension glaucoma (NTG) and fellow preperimetric NTG showing only inferotemporal retinal nerve fiber layer (RNFL) defect in red-free RNFL photography in both eyes. We also enrolled 9 healthy controls. Using OCT-A, radial peripapillary capillary densities at inferotemporal and superotemporal regions were evaluated. Paired comparison of peripapillary vessel density was performed for PG eye, PPG eye, and normal eye. RESULTS: A total of 26 eyes of the 13 patients with unilateral PG and fellow PPG eyes and 18 eyes of 9 normal controls were analyzed. Vessel densities at the whole peripapillary region and inferotemporal region in PG eyes were significantly lower than those in PPG eyes (P = 0.001, P<0.001, respectively). Comparison between PPG and normal eyes showed no significant difference in the whole peripapillary region or the inferotemporal region (P = 0.654, P = 0.174, respectively). There was no significant (P = 0.288) difference in vessel density at superotemporal region among the three types of eyes (PG eye, PPG eye, and normal eye). CONCLUSION: PPG eyes and normal eyes were found to have the similar densities of peripapillary microvasculature at the area with nerve fiber layer defect, whereas in PG eye, there was a significant decrease in vessel density at the area of RNFL thinning. This provides evidence that microvascular compromise in the retina might be a secondary change to nerve fiber layer degeneration in the pathogenesis of NTG.