@media
  only screen and (-webkit-min-device-pixel-ratio: 2),
  only screen and (min--moz-device-pixel-ratio: 2),
  only screen and (-o-min-device-pixel-ratio: 2/1),
  only screen and (min-device-pixel-ratio: 2),
  only screen and (min-resolution: 192dpi),
  only screen and (min-resolution: 2dppx){ 

  /* Retina stuff here */

}