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. 113View Equation 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.