phosphenes

phosphenes - n., visual sensations arising from mechanical stimulation by pressure upon the eyeball when the lids are closed.


Or by other methods, such as electrical stimulation, or seeing stars after a sneeze. Seeing things without light. One spot of light would be a phosphene, but they never come in singletons, in my experience. From French phosphène, from Greek roots phōs, light + phainein, to cause to appear, to show.

---L.