Abstract: An apparatus is provided for the measurement of the velocity of blood flowing within a blood vessel of an eye wherein the apparatus includes a light source for producing a source beam of light and an optical element for applying the source beam of light to the blood vessel to permit the blood flowing within the blood vessel to scatter a portion of the source beam of light and produce bidirectional scattered beams. A detector system for detecting the bidirectional scattered beams provides signals representative of the scattered beams. The light source and the detector system are disposed in a confocal relationship. An output representative of the velocity of the blood flow velocity is produced in accordance with the signals. The light source and the detector system include respective pinholes wherein the respective pinholes are disposed in the confocal relationship. The blood vessel is conjugate with the respective pinholes of the light source and the detector system.

Abstract: A method for determining the speed of leukocytes in retinal capillaries comprises the steps of simulating, by means of a minicomputer system which includes a visual display, the motion of entoptically seen leukocytes in retinal capillaries; observing entoptically the motion of actual leukocytes in the retinal capillaries of the subject's own eye; and comparing the appearances and motions of the visual display and the actual leukocytes. Apparatus for performing such a method comprises a minicomputer, a graphic display, and a display-processor interface.

Abstract: A method for determining the speed of leukocytes in retinal capillaries comprises the steps of simulating, by means of a minicomputer system which includes a visual display, the motion of entoptically seen leukocytes in retinal capillaries; observing entoptically the motion of actual leukocytes in the retinal capillaries of the subject's own eye; and comparing the appearances and motions of the visual display and the actual leukocytes. Apparatus for performing such a method comprises a minicomputer, a graphic display, and a display--processor interface.

Abstract: A bidirectional laser Doppler velocimeter provides absolute measurement of the speed of red blood cells flowing in individual retinal vessels. A standard retinal camera is used, and the need for a contact lens for the subject eye is eliminated. The laser beam is delivered to the eye through the fundus illumination optical system of the camera. Target fixation is done with the eye under examination. The measurements are independent from the ocular refraction; only the axial length of the eye need be determined. The instrument markedly simplifies the technique of retinal blood flow measurement.

Abstract: A beam of laser light is impinged on a vessel or vessels in which blood is flowing, such as vessels in the retina of the eye. The reflected light is detected with a photodetector to product a signal representative of the Doppler shift frequencies of the light scattered from the moving blood cells. If the light is impinged on a capillary bed the photodetector produces a homodyne type signal, from light reflected from blood in the various capillaries; if the light is impinged on a single vessel the photodetector produces a heterodyne type signal from the light reflected from the vessel wall and the light reflected from the blood cells flowing in the vessel. The signal from the photodetector is amplified and used to drive an audio output to produce a sound representative of the velocity of the blood.