  Vortices are screw phase dislocations associated with helicoidal wave-fronts.
In nonlinear optics, vortices arise as singular solutions to the
phase-intensity equations of geometric optics. They exist for a general class
of nonlinear response functions. In this sense, vortices possess a universal
character. Analysis of geometric optics equations on the hodograph plane leads
to deformed vortex type solutions that are sensitive to the form of the
nonlinearity. The case of a Kerr type nonlinear response is discussed as a
specific example.
