  Using a new geometrical approach introduced by Gibbons and Werner we study
the deflection angle by Reissner-Nordstr\"{o}m black holes in the background
spacetimes with a global monopole and a cosmic string. By calculating the
corresponding optical Gaussian curvature and applying the Gauss-Bonnet theorem
to the optical metric we find the leading terms of the deflection angle in the
weak limit approximation. We find that the deflection angle increases due to
the presence of topological defects.
