  We consider the impact of second order corrections to the geodesic equation
governing gravitational lensing. We start from the full second order metric,
including scalar, vector and tensor perturbations, and retain all relevant
contributions to the cosmic shear corrections that are second order in the
gravitational potential. The relevant terms are: the nonlinear evolution of the
scalar gravitational potential, the Born correction, and lens-lens coupling. No
other second order terms contribute appreciably to the lensing signal. Since
ray-tracing algorithims currently include these three effects, this derivation
serves as rigorous justification for the numerical predictions.
