  A first principles approach is presented for calculations of optical --
ultraviolet (UV) spectra including excitonic effects. The approach is based on
Bethe-Salpeter equation calculations using the \textsc{NBSE} code combined with
ground-state density-functional theory calculations from the electronic
structure code \textsc{ABINIT}. Test calculations for bulk Si are presented,
and the approach is illustrated with calculations of the optical spectra and
birefringence of $\alpha$-phase SiO$_2$ and the rutile and anatase phases of
TiO$_2$. An interpretation of the strong birefringence in TiO$_2$ is presented.
