Determining the redshift of astronomical sources is fundamental for cosmological studies, since it allows deriving distances to the observer. However, the distance-redshift relationship commonly used is obtained from the isotropic, homogeneous Friedmann-Lemaitre-Robertson-Walker (FLRW) metric. By fitting this distance-redshift relations to Supernovae Ia data, used by many authors as standard candles for distance measurements, it was shown that the expansion of the universe is accelerating, since the addittion of equations of state in the cosmological model was required. Whether this dark energy is a cosmological constant or a quintessence is still to be determined, and is the objective of some current and future dark energy studies. However, the Universe is not homogeneuos. The gravitational lens effect changes the luminosity of distant sources, and it may also change significantly the angular diameter distance, thus modifying the luminosity distance, changing the distance-redshift relation with respect to that of an homogeneous universe. This effect can be considered an additional source of dispersion of the data, affecting the determination of the dark energy equation of state. We are developing a test for studying departures from the FLRW distance-redshift relation, and its impact on the determination of the dark energy equation of state.