  Astrometric observations of microlensing events were originally proposed to
determine the lens proper motion with which the physical parameters of lenses
can be better constrained. In this proceeding, we demonstrate that besides this
original usage astrometric microlensing observations can be additionally used
in obtaining various important information about lenses. First, we demonstrate
that the lens brightness can be determined with astrometric observations,
enabling one to know whether the event is caused by a bright star or a dark
lens. Second, we show that with additional information from astrometric
observations one can resolve the ambiguity of the photometric binary lens fit
and thus uniquely determine the binary lens parameters. Finally, we propose two
astrometric methods that can resolve the degeneracy in the photometric lens
parallax determination. Since one can measure both the proper motion and the
parallax by these methods, the lens parameters of individual events can be
uniquely determined.
