  We study the helicity amplitudes of the process \gamma \gamma \to \gamma
\gamma at high energy, which in the standard and SUSY models first arise at the
one-loop order. In the standard model (SM), the diagrams involve W and charged
quark and lepton loops, while in SUSY we also have contributions from chargino,
charged sfermion and Higgs loop diagrams. The SUSY contributions are most
important in the region above the threshold for producing the supersymmetric
partners; since there, they interfere most effectively with the primarily
imaginary SM amplitudes. Simple expressions for the relevant 1-loop functions
are given, which provide a direct overview of the behaviour of the helicity
amplitudes in the whole parameter space at high energies. The various
characteristics of a large set of observables are studied in detail.
