He said he had never made an optogram, but he imagines what those last images were,
The process of making an optogram is by blindfolding the person, rabbit or frog.
Optogram appears as a white image on a red or purple background.
He added that a good description of an optogram is that when you lean up against an object and you get that imprint on your skin, "it is not what you are thinking, it is not necessarily what you are seeing, but what your retina is receiving even if you were daydreaming.
It includes exhibits such as a very detailed recreation of what he imagines Kuhne's laboratory looked like, photos of rabbit optograms from 1975, various anatomically accurate sketches of eyes that have been manipulated to include small humanoids and many other exhibits that relate to eyes and the moments before death.
It is not surprising that both Jules Claretie, in L'Accusateur, and Jules Verne, in Les Freres Kip, cite "le pourpre retinien"--retinal violet--as the motivating fact for their optogram mysteries.
Evans explains in his article about optogram fictions, the scientific experiments leading to the discovery of retinal violet were made available widely to the French public of the fin-de-siecle through various newspapers, journals, and popular gazettes (341-43).