However, by this we do not mean that the MOND lensing can be computed from the projected surface
density on the lens-plane as in GR, because the convergence parameter (Eq. 113 below) is not a measure of the
projected surface density anymore. This is also sometimes referred to as the “thin-lens approximation” in GR,
and is not valid in MOND: two lenses with the same projected surface density can have different convergence
parameters, because lensing also depends strongly on the distribution of the source mass along the line-of-sight in
MOND.