[Comparative measurement of optic nerve head circulation using laser speckle circulation analyser of ocular fundus...

The microcirculation in the optic nerve head (ONH) was measured using the recently developed laser speckle circulation analyser for the ocular fundus. The measurements were compared to those of the capillary blood flow (CBF) obtained by the hydrogen clearance method. The ONH blood flow was measured using both methods simultaneously in six normal albino rabbits. The blood flow was increased by inhalation of carbon dioxide (CO2) and reduced by systemic administration of endothelin-1 (ET-1). 10%CO2 inhalation showed a CBF increase of about 22% in the ONH in the hydrogen clearance method, and intravenous injection of ET-1 at 10(-10) mol/kg decreased the reading by about 19%. A significant correlation (r = 0.92, p < 0.01) was found between the relative values of NB (Normalized blur, by laser speckle method) and CBF in the ONH. This result indicates that the change of NB in the ONH shares the same accuracy as hydrogen clearance method within the range of our present experiment. This study provides a fundamental basis for the clinical application of the laser speckle method in measuring ONH circulation.