phos·phene 
(fŏsfēn′)
(fŏsfēn′)n.
A sensation of light caused by excitation of the retina by mechanical or electrical means rather than by light, as when the eyeballs are pressed through closed lids.
[French phosphène : Greek phōs, light; see PHOS- + Greek phainein, to cause to appear, to show; see bhā-1 in the Appendix of Indo-European roots.]