  We discuss the peculiarities of gravitational lensing by spherically
symmetric wormholes if they are not symmetric with respect to their throats. It
is noticed, in particular, that wormholes always contain the so-called photon
spheres, near which the photon deflection angles can be arbitrarily large, but,
in general, the throat is such a sphere only for symmetric wormholes. In some
cases, photons from outside can cross the throat and return back from a
neighborhood of a photon sphere if the latter is located beyond the throat. Two
families of generally asymmetric wormhole configurations are considered as
examples: (1) anti-Fisher wormholes with a massless phantom scalar field as a
source of gravity, and (2) wormholes with a zero Ricci scalar that may be
interpreted as vacuum configurations in a brane world. For these metrics, the
photon effective potentials and deflection angles are found and discussed.
