  A study is presented to extend the measurements of photon-photon scattering
in ultra-peripheral Pb-Pb collisions at the LHC into the mass region of the
pseudoscalar resonances $\eta$ and $\eta'$. The elementary photon-photon
scattering cross section is presented. The cross section for photon-photon
scattering in Pb-Pb is derived by convoluting the elementary photon-photon
cross section with the Pb-Pb photon luminosity. The main background to
two-photon final states, arising from double $\pi^{0}$ production with two of
the four decay photons escaping detection, is examined, and possible
kinematical conditions are discussed to optimize the signal-to-background ratio
for such measurements at mid-rapidity.
