  We study the notion of optical geometry, defined to be a Lorentzian manifold
equipped with a null line distribution, from the perspective of intrinsic
torsion. This is an instance of a non-integrable version of holonomy reduction
in Lorentzian geometry. These generate congruences of null curves, which play
an important r\^{o}le in general relativity. Conformal properties of these are
investigated. We also extend this concept to generalised optical geometries as
introduced by Robinson and Trautman.
