The advent of imagers with integrated linear polarization selectivity opens new opportunities for researchers interested in the polarization properties of biological tissues. In this Letter, we explore the mathematical framework necessary to obtain common parameters of interest: azimuth; retardance; and depolarization with reduced Mueller matrices that can be measured with the new instrumentation. We show that in the case of acquisition close to the tissue normal, simple algebraic analysis of the reduced form of the Mueller matrix yields results very close to those obtained with more complex decomposition algorithms applied to a complete Mueller matrix.