  Gravitational lensing by the light sphere of compact objects like black holes
and wormholes will give us information on the compact objects. In this paper,
we provide an improved strong deflection limit analysis in a general
asymptotically flat, static, spherically symmetric spacetime. The strong
deflection limit analysis also works in ultrastatic spacetimes. As an example
of an ultrastatic spacetime, we reexamine the deflection angle in the strong
deflection limit in an Ellis wormhole spacetime. Using the strong deflection
limit, we obtain the deflection angle analytically for the Reissner-Nordstrom
spacetime. The point of the improvement is the definition of a standard
variable in the strong deflection limit analysis. We show that the choice of
the variable is as important as the choice of the coordinates and we conclude
that one should choose a proper variable for a given spacetime.
