  Based on the principle of the Lorentz covariance the transition matrix
elements from an off-shell photon state to the vacuum are decomposed into the
light-cone photon DAs, in which only two transversal DAs survive in the
on-shell limit. The eight off-shell light-cone photon distribution amplitudes
(DAs) corresponding to chiral-odd and chiral-even up to twist-four and the
corresponding coupling constants are studied systematically in the instanton
vacuum model of quantum chromodynamics (QCD). The various individual photon DA
multiplied by its corresponding coupling constant is expressed in terms of the
correlation functions, which are connected with the spectral densities of an
effective quark propagator, and then evaluated in the low-energy effective
theory derived from the instanton vacuum model of QCD. The explicit analytical
expressions and the numerical results for the photon DAs and their coupling
constants are given.
