Optic Nerve Head Blood Flow Measured by Laser-Doppler Flowmetry

Abstract

The optic nerve head (ONH) is supplied by two main sources of blood flow: the superficial layers by the central retinal artery (CRA) and the deeper layers by the posterior ciliary arteries (PCAs). Using a fundus camera-based laser-Doppler flowmetry (LDF) technique to measure blood flow in the ONH tissue, we conducted a study in rhesus monkey eyes to obtain a better understanding of which part of the ONH circulation is measured by LDF. LDF measurements were taken at baseline, then after experimental occlusion of CRA (12 eyes), all the PCAs (9 eyes) and combined occlusion of CRA and all the PCAs (9 eyes). ONH, choroidal and retinal circulations following the various arterial occlusions were investigated by fluorescein fundus angiography. Average LDF flow during CRA occlusion alone was highly significantly decreased (p 0.20). After PCA occlusion alone, however, measurements showed a non-significant increase in LDF flow of 17±37%. Thus, the findings of this study suggest that the LDF technique is predominantly sensitive to flow changes in the surface layer of the ONH and less sensitive to those in the deeper layers of the ONH.