Method and apparatus for measuring retinal blood flow

Claim 1

Apparatus for measuring retinal blood flow comprising a laser for producing a beam of radiation, means for directing a single beam of the laser radiation along an optical path into an eye and onto a retinal blood vessel, a detector for detecting laser radiation reflected from blood corpuscles within the blood vessel, and for producing a doppler output signal, means for directing laser radiation reflected by the eye into the detector, means for variably deflecting the laser radiation across the optical path to enable the desired part of the retinal blood vessels to be illuminated by the laser radiation and defining an acceptance angle, a light source for general illumination of the fundus of the eye, means for observing light and laser radiation reflected by the eye and for determining the angle of the blood vessel, the doppler angle of the blood vessel being determined from said acceptance angle and said angle of the blood vessel, whereby the laser radiation may be directed along the optical path and onto the retinal blood vessel and the laser radiation reflected from the blood vessel is reflected back along the optical path into the detector to determine the doppler shift of laser radiation and hence blood flow velocity from the value of the doppler output signal and from the doppler angle defined by said acceptance angle and said angle of blood vessel.