Multilayered refractive data storage allows serial optical recording at data densities exceeding 1012bits/cm3. Data may be recorded in a write once mode using two-photon excitation of a photopolymer film. Data is read with minimal cross-talk between layers by wavefront shearing interferometry, for example by differential interference contrast microscopy. The readout signal from such a multilayered refractive memory initially increases with the refractive index contrast. However, high index contrast may eventually lead to excessive scattering which could reduce signal quality. We report here an empirical method for quantitatively assessing the readout performance of multilayer refractive memory media using laser scanning differential interference contrast microscopy and simple image processing. Signal level distributions for a multilayered refractive write once data storage structure are presented.