The Retinal Implant Viddy Machine was a machine that could teach entire subjects within a few minutes. The Doctor found it either on the planet Flogstrune or Mobeli-Four.
Two of the Viddy-Reels that played on the machine were Advanced High School Physics, which the Doctor intended to show Sharon Davies to help her keep up with her school work; and The Galactic Crime-Fighter's Notebook, which Sharon ended up viewing by mistake, and which she described as "smashing" and really good", much to the Doctor's puzzlement. (COMIC: Doctor Who and the Time Witch)