  The pattern of lepton mixing can emerge from breaking a flavor symmetry in
different ways in the neutrino and charged lepton Yukawa sectors. In this
framework, we derive the conditions imposed on the mixing matrix by the
structure of discrete groups of the von Dyck type which include A4, S4 and A5.
We show that, in general, these conditions reduce to two equations for the
mixing parameters (angles and CP phase \delta). These constraints, which
correspond to unbroken residual symmetries, are consistent with non-zero 13
mixing and deviations from maximal 2-3 mixing. For the allowed values of mixing
angles we predict \delta = 60 - 90^{\circ}.
