We propose a quantum algorithm that simulates the propagation of a light field through a weakly inhomogeneous medium. In the paraxial approximation, the wave equation in an inhomogeneous material takes the form of the Schrödinger equation with a time-dependent Hamiltonian. This reduction is used to simulate wave optical dynamics on a quantum computer. Beam propagator operators for a short propagation distance are constructed using an efficient and flexible block-encoding that enables the simulation of various optical setups. The algorithm is showcased by simulating the propagation of a one-dimensional Gaussian beam through a lens of finite thickness, and the resulting spherical aberration is demonstrated.