The American College of Optometrists has [a page on this alleged phenomenon, called "optograms"][1]. They claim that *with chemical fixatives and immediate extraction of the retina*, one can discern a rough image representing the last image exposed on the retina. This is vaguely plausible, since the formation of an image does induce chemical changes in the retina. 

In the mid-17th Century, a Jesuit friar named Christopher Schiener did some experiments on frogs [[Ref](]; later [Wilhelm Kühne (a physiologist of some repute)][2] did [similar experiments on rabbits][3]. 

The College go so far as to say:

> The one and only case of a 'Human Optogram' is therefore that of
> Erhard Gustav Reif in November 1880....[H]e was executed by guillotine in the prison
> yard in the small German town of Bruchsal. His left eye was extracted
> within ten minutes of the sentence being carried out. Reif's optogram,
> some 4mm in height, does not survive, merely a simple sketch drawing
> taken from it.... It has a superficial resemblance to a
> guillotine blade although the victim's eyes were bandaged seconds
> before the blade fell. Possibly they are the steps he had to ascend
> shortly beforehand.

In 1975 [a group of German scientists in Heidelberg reproduced the original rabbit research][4]. It seems that they were able to produce rough images, but concluded that the technique had no forensic or scientific value.