 A newly developed compact laser Doppler flowmeter LDF allows the measurement of blood flow at the level of the neuroretinal rim of the optic nerve. This system delivers a laser beam from a diode laser 670 nm to a discrete site at the optic nerve head. The scattered light is collected by an optical fiber with the image of its aperture approximately 150 μm in diameter focused onto the illuminated site. This fiber guides the scattered light to a photodetector. An area of the fundus 30 in diameter is illuminated in red-free light for observation of the fundus and positioning of the laser beam. This instrument detects the light scattered by the red blood cells RBCs within an annulus centered on the illumination site of the laser. This flowmeter consists of a self-aligned confocal system, a fundus illumination green light and CCD based observation unit, a target fixation system and a CCD camera to observe the pupil. This CCD allows monitoring of the position of the probing laser beam at the pupil to insure constant entrance point in successive measurements of ONH blood flow. The Doppler signal is digitized and a dedicated software operating on a portable computer calculates the relative velocity VEL, volume VOL and flow of the red blood cells in the eye microcirculation. Synchronization of these parameters with the heart pulse allows determination of the flow pulsatility. For the investigation of the effect of increased retinal activity on optic nerve blood flow, a system for delivering visual stimuli flicker has been adapted to the fundus camera-based instrument. 