The general trend for miniaturization leads to widespread use of micro-optical elements for various applications including optical communications, embedded photonic systems, beam shaping and imaging. We propose here a cost-effective manufacturing method for complex 3D micro-optics based on femtosecond laser-manufactured of simple glass preforms that are topologically transformed into complex 3D objects with optical surface quality through a localized laser-induced viscous flow of the surface. Using this principle, we show that non-trivial shapes with non-rotational symmetry can be obtained. Finally, we introduce a simulation framework that predicts the topological transformation of these objects that we compare to the actual surface and optical properties of the experimentally produced specimens.