  Observed magnitudes of many quasars with redshifts exceeding $z=5$ correspond
to luminosities $L_{\rm bol} > 10^{14}\,L_\odot$. The standard mechanism of
quasar energy release by accretion suggests that masses of superluminous
quasars should exceed $10^{10}\,M_\odot$. On the other hand, the age of these
objects in the standard cosmological model is below one billion years, which is
too short to explain their formation in the early Universe. Many quasars are
known to be gravitationally lensed; showing multiple images of the same object.
In the case of remote quasars with no multiple images, it is still possible
that they are also gravitationally lensed by foreground objects of intermediate
masses, such as globular clusters or dwarf galaxies. Such mesolensing would
result in essential amplification of quasar brightnesses, subject to
geometrical configuration between the lens and the lensed object. Here we
estimate the fraction of quasars whose brightness might have been amplified by
gravitational lensing.
