  We study the Mass Discrepancy-Acceleration Relation (MDAR) of 57 elliptical
galaxies by their Einstein rings from the Sloan Lens ACS Survey (SLACS). The
mass discrepancy between the lensing mass and the baryonic mass derived from
population synthesis is larger when the acceleration of the elliptical galaxy
lenses is smaller. The MDAR is also related to surface mass density
discrepancy. At the Einstein ring, these lenses belong to high-surface-mass
density galaxies. Similarly, we find that the discrepancy between the lensing
and stellar surface mass density is small. It is consistent with the recent
discovery of dynamical surface mass density discrepancy in disk galaxies where
the discrepancy is smaller when surface density is larger. We also find
relativistic modified Newtonian dynamics (MOND) can naturally explain the MDAR
and surface mass density discrepancy in 57 Einstein rings. Moreover, the
lensing mass, the dynamical mass and the stellar mass of these galaxies are
consistent with each other in relativistic MOND.
