Coherent optical techniques for diagnostics of retinal blood flow

Up to now, a variety of coherent optical techniques have been proposed and extensively studied for diagnostics of the retinal blood flow. These techni ques are mainly based on dynamic laser light-scattering phenomena such as t he laser Doppler effect and the laser speckle fluctuation. This paper revie ws, first, spectral reflectance properties of the ocular fundus tissue laye rs and, then, principles of the techniques with the comparison of the Doppl er and the speckle methods. Some physical phenomena are also discussed in t he origin of the techniques such as heterodyne and homodyne beatings, and t ime-varying speckles. Developing processes of each technique are briefly ou tlined. Peculiarities of blood flow measurements at the retina are finally examined from the methodological point of view. (C) 1999 Society of Photo-O ptical Instrumentation Engineers. [S1083-3668(99)02001-8].