  Compact radio sources have been observed to undergo large, frequency
dependent changes in intensity due to lensing by structures in the interstellar
medium, in so-called "extreme scattering events" (ESEs). While the study of
astrophysical plasma lensing has primarily focused on the geometric limit of
optics, coherent radio sources such as pulsars exhibit wave effects when
lensed. The additional phase information provided by interference effects in
the wave regime may yield more information about the lens than could be
obtained in the geometric regime. In this paper, we show that, using wave
effects, one can potentially distinguish a one-dimensional lens (where
"one-dimensional" includes both highly elongated lenses, as well as perfectly
axisymmetric lenses) from a fully two-dimensional lens, with minimal
assumptions on the form of the lensing potential.
