  The currently released datasets of the observational surveys reveal the
redshift dependence of the physical features of cosmic voids. We study the void
induced hyperbolicity, that is the deviation of the photon beams propagating
the voids, taking into account the redshift dependence of the void size
indicated by the observational surveys. The cumulative image distortion
parameter is obtained for the case of a sequence of variable size voids and
given underdensity parameters. The derived formulae applied along with those of
redshift distortion ones, enable one to trace the number and the physical
parameters of the line-of-sight voids from the analysis of the distortion in
the galactic surveys.}
