Spectral dependence of the pseudodielectric function ε(E)=ε1(E)+iε2(E) as well as of the complex refractive index, extinction coefficient, absorption coefficient, and normal-incidence reflectivity of Cu2In4Se7 and CuGa3Se5 ordered vacancy compound crystals are modeled in the 0.8–4.4eV photon energy range using a modification of Adachi’s model [T. Kawashima et al. J. Appl. Phys. 84, 5202 (1998)] for optical properties of semiconductors. Model parameters are determined using the acceptance-probability-controlled simulated annealing method. Excellent agreement with experimental data is obtained; the relative errors for the real ε1 and for imaginary ε2 part of the dielectric function are equal to 0.9%–1.5% and 3.2%–4.1% for the studied compounds.