  We give precise details to support that observations of gravitational lensing
at scales of individual, groups and clusters of galaxies can be understood in
terms of non-Newtonian gravitational interactions with a relativistic structure
compatible with the Einstein Equivalence Principle. This result is derived on
very general grounds without knowing the underlying structure of the
gravitational field equations. As such, any developed gravitational theory
built to deal with these astrophysical scales needs to reproduce the obtained
results of this article.
