 - experimental setting: The stimulus is a pure green luminance flicker generated by an array of ultrabright light-emitting diodes with dominant wavelengths at 524 nm and located in the plane of the light source of the fundus camera. The diodes are synchronously square-wave modulated at 15 Hz between 0 and 10 lux. The stimulus is delivered to the eye in Maxwellian view through the fundus illuminations optical system of the camera Topcon Optical, Tokyo, Japan and it uniformly illuminates a 25 diameter area that included both the fovea and the optic disc. Blood flow is measured at baseline before the flicker stimulation, and then during the 2 min period of flicker stimulation. 