Light propagation in tissues is governed by the theory of radiative transport. The radiative transport equation takes into account absorption and scattering due to inhomogeneities. A two-layer medium is a useful model for tissues because it accounts for the differences in optical properties between the superficial and deep regions of tissues. We are interested in probing only the superficial layer because most pre-cancerous tissues develop there. To do this we introduce an alternate boundary condition that allows for the removal of the bottom layer from the problem. For the case when the top layer is thin, we compute an asymptotic solution. We validate our results by comparing them with numerical solutions.