  A fundamental quantity in multiple scattering is the transport mean free path
the inverse of which describes the scattering strength of a sample. In this
paper, we emphasize the importance of an appropriate description of the
effective refractive index $n_{\mathrm{eff}}$ in multiple light scattering to
accurately describe the light transport in dense photonic glasses. Using
$n_{\mathrm{eff}}$ as calculated by the energy-density coherent potential
approximation we are able to predict the transport mean free path of
monodisperse photonic glasses. This model without any fit parameter is in
qualitative agreement with numerical simulations and in fair quantitative
agreement with spectrally resolved coherent backscattering measurements on new
specially synthesized polystyrene photonic glasses. These materials exhibit
resonant light scattering perturbed by strong near-field coupling, all captured
within the model. Our model might be used to maximize the scattering strength
of high index photonic glasses, which are a key in the search for Anderson
localization of light in three dimensions.
