Basal blood flow and autoregulation changes in the optic nerve of rhesus monkeys with idiopathic bilateral optic atrophy.

PURPOSE: To characterize the hemodynamic features and the association with structural damage in the optic nerve head (ONH) of idiopathic bilateral optic atrophy (BOA) in rhesus macaque monkeys.
METHODS: In five animals with BOA and nine healthy animals under general anesthesia (pentobarbital), intraocular pressure (IOP) was manometrically controlled. ONH blood flow was measured with a laser speckle flow graph device. Basal blood flow in global and quadrantal sectors was measured with IOP set at 10 mm Hg; autoregulation capacity was assessed by comparing blood flow changes before and after IOP was increased from 10 to 30 mm Hg. Spectral-domain optic coherence tomography was used to measure retinal nerve fiber layer thickness (RNFLT) by peripapillary circular scans.
RESULTS: Compared with control eyes, RNFLT in BOA eyes was significantly less in all sectors (P < 0.001) except the nasal (P = 0.25); the average global and sectoral blood flow in all quadrants was significantly lower (P < 0.001). These blood flow changes were significantly correlated with corresponding sectoral RNFLT (P < 0.01) except the nasal (P = 0.25). After IOP was increased to 30 mm Hg, global blood flow was significantly reduced (P < 0.001), but with no regional preferences despite prominent temporal RNFLT loss; no significant blood flow change was observed in control eyes (P = 0.24).
CONCLUSIONS: Basal blood flow and autoregulation capacity in the ONH of BOA were significantly compromised, with a close correlation to structural changes. The hemodynamic changes showed no regional preference across the ONH, which was consistent with postmortem histological observations.