  Microlensing and occultation are generally studied in the geometric optics
limit. However, diffraction may be important when recently discovered
Kuiper-Belt objects (KBOs) occult distant stars. In particular the effects of
diffraction become more important as the wavelength of the observation and the
distance to the KBO increase. For sufficiently distant and massive KBOs or Oort
cloud objects not only is diffraction important but so is gravitational
lensing. For an object similar to Eris but located in the Oort cloud, the
signature of gravitational lensing would be detected easily during an
occultation and would give constraints on the mass and radius of the object.
