The Lorentz—Lorenz formula and the Ewald—Oseen extinction theorem in an inhomogeneous medium have been derived from rigorous dispersion theory. The electric field that is scattered by an inhomogeneous medium is also determined by the application of the theory. This expression of the scattered field seems to show the relation between dispersion theory and diffraction theory.
TAKASHI SUZUKI, "Derivation of Diffraction Theory from Rigorous Dispersion Theory," J. Opt. Soc. Am. 61, 1029-1034 (1971)