Retinal blood-flow visualization by means of laser speckle photography

We present the preliminary findings of an investigation into the visualization of retinal blood-flow distribution by means of single-exposure laser-speckle photography. The technique relies on the speckle effect produced when laser light is scattered at a diffusing surface and on the fact that the speckle will be averaged out to some extent when the surface concerned is moving. Spatial filtering techniques are used enhance the resulting variations in speckle contrast. The method is noncontacting and noninvasive, properties shared with the laser Doppler anemometry technique. Although it is less quantitative than the Doppler technique, it does have the advantage of giving an overall map of blood velocities instead of point measurements only, and we offer it as a complementary technique.