Partial Transmutation of Singularities in Optical Instruments
  Some interesting optical instruments such as the Eaton lens and the Invisible Sphere require singularities of the refractive index for their implementation. We show how to transmute those singularities into harmless topological defects in anisotropic media without the need for anomalous material properties. 
Janos Perczel, Ulf Leonhardt
physics.optics