  In this paper the two-photon interactions at high energies are investigated
considering different approaches for the QCD dynamics. In particular, we
calculate the $\gamma^* \gamma^*$ total cross section in different theoretical
approches and present a comparison among the predictions of the BFKL dynamics
at leading and next-to-leading order with those from saturation physics. We
analyze the possibility that the future linear colliders could discriminate
between these different approaches.
