Lorentz geometry represents the mathematical foundation of Einstein’s general relativity. From the concept of the cone of edge rays, it was introduced successfully in the study of homogeneous media nonimaging optics, Gutiérrez et al. (1996), Winston et al. (2005). In this paper we present a new Lorentzian geometry formalism to analyze optical systems with refractive elements. We have obtained the general system of partial differential equations and the integrability conditions to be fulfilled. This new mathematical formalism is the basis for a new optical technique to analyze the irradiance pattern produced by refractive optical systems. We apply this Lorentzian formalism to an optical media with exponential refraction index. Comparisons between irradiance patterns obtained by this formalism and by raytrace simulations are also presented.