We investigate an effective low energy theory of HgTe quantum wells near their mass inversion thickness in a perpendicular magnetic field. By comparison of the effective band structure with a more elaborated and well-established model, the parameter regime and the validity of the effective model are quantified. Optical transitions (between Landau levels) in HgTe quantum wells are analyzed. We find selection rules which we functionalize to optically manipulate edge state transport. [1] In the absence of magnetic fields, the ballistic transport through HgTe quantum wells in the so-called inverted regime is believed to be dominated by edge state transport. The existence of these edge states (at zero magnetic field) is one of the hallmarks of topological insulators. We show that transport through the gapped bulk via evanescent modes can in general not be neglected in ballistic HgTe quantum wells. [1] M.J. Schmidt, E.G. Novik, M. Kindermann, and B. Trauzettel, Phys. Rev. B 79, 241306(R) (2009)