Caustic Crossings in Quasar Light Curves?
  Numerical simulations and theoretical studies of the gravitational microlensing effect of a population of small bodies distributed along the line of sight to a compact light source such as a quasar indicate that caustic crossing effects will be present given a sufficiently large optical depth to lensing. These events will produce characteristic patterns in the quasar light curve. In this paper we use a large sample of quasar light curves to search for features with the properties of caustic crossing events. Two good candidates are presented which it is argued are not easily explained as intrinsic variation of the uasars. The relation between these events and microlensing featurees seen in multiple quasar systems is discussed, as well as the implications for the dark matter problem of a population of microlensing bodies. 
M.R.S. Hawkins