  In this work it is shown that vascular structures of the human retina
represent geometrical multifractals, characterized by a hierarchy of exponents
rather then a single fractal dimension. A number of retinal images from the
STARE database (www.parl.clemson.edu/stare) are analyzed, corresponding to both
normal and pathological states of the retina. In all studied cases a clearly
multifractal behavior is observed, where capacity dimension is always found to
be smaller then the information dimension, which is in turn always smaller then
the correlation dimension, all the three being significantly lower then the DLA
(Diffusion Limited Aggregation) fractal dimension. We also observe a tendency
of images corresponding to the pathological states of the retina to have lower
generalized dimensions and a shifted spectrum range, in comparison with the
normal cases.
