Measurement of retinal microvascular pulsation from SLO image sequences

Image sequences from a scanning laser ophthalmoscope (SLO) provide noninvasive data sets that may be used to analyze retinal pulsation processes. For example, the venous pulse, commonly observed at or near the edge of the optical disk, is thought to be induced by the cyclic pulsatility of intraocular pressure, however more recent studies R. Attariwala et al. (1999) have suggested that venom pulsation is induced from flow rather than pressure processes at or near the optical disk. This paper describes the image sequence analysis techniques originally developed to support the studies of R. Attariwala et al. (1999) which hypothesized that the venous pulse should exhibit exponential decay of amplitude with distance along a vessel away from the optical disk. The proposed algorithms estimate the width of retinal vessels relative to distance along the vessel over time and in the presence of both slow drift and severe saccadic eye motion. Feature tracking methods are used to estimate image motion so that vessel cross-sections can be extracted at consistent distances along the vessel. Amplitude of the fundamental vessel pulsation is then estimated relative to distance along the vessel. The proposed methods provide an automated approach for measurement of temporal microvascular pulsation processes. Results are given for real SLO image sequences and are consistent with the hypotheses proposed in R. Attariwala et al. (1999).