  We discuss the measured partial width of the pseudoscalar charmonium state,
$\eta_c$, into two photons. Predictions from potential models are examined and
compared with experimental values. Including radiative corrections, it is found
that present measurements are compatible both with a QCD type potential and
with a static Coulomb potential, with $\alpha_s$ evaluated at two loops.
Results are also compared with those from $\jpsi$ data through the NRQCD model.
