Abstract
Purpose :
The choroidal watershed and parapapillary hypoperfusion zones are regions of reduced blood flow that are also shared with the blood supply to the prelaminar optic nerve and may be vulnerable to decreases in perfusion pressure in NAION and glaucoma. We sought to establish the degree of reduced blood flow in these parapapillary choroidal regions and the corresponding sectors of the optic nerve head using laser speckle flowgraphy (LSFG).
Methods :
A case-control study of 48 patients with NAION and 28 control subjects were studied using LSFG. In a subset of eyes, fluorescein angiography was used to spatially correlate the location of the choroidal hypoperfusion zones with LSFG. Blood flow was compared between the areas within and outside of the choroidal hypoperfusion zone and its relation to blood flow in adjacent corresponding sectors of the optic nerve head.
Results :
Blood flow within the choroidal hypoperfusion zone was reduced to 50.6 ± 16.5% (mean ± SD) of blood flow in the adjacent choroid, outside of the hypoperfusion zone. Besides a highly significant correlation between blood flow in sectors of the optic nerve rim tissue and adjacent peripapillary choroid, blood flow was significantly lower in rim sectors on the temporal side of the nerve compared to the nasal side (p=0.0001), especially when the parapapillary choroidal hypoperfusion zone was located more temporal to the center of the optic nerve.
Conclusions :
Blood flow is significantly lower in the choroidal watershed and parapapillary hypoperfusion zones, making its vascular bed more vulnerable to dips in ocular perfusion pressure. The spatial location of the choroidal watershed and parapapillary hypoperfusion zone relative to the optic nerve head and its shared blood supply with the prelaminar optic nerve may impart additional risk to those nerve sectors lying within it in ischemic disorders of the optic nerve.
This is a 2020 ARVO Annual Meeting abstract.