It has been said a dead person can help solve a murder. Is it true that you can take out a dead person’s eye and use it to find out the last person or thing he or she saw, and thus maybe identify the killer?

Question

A. Yes, because photoreceptors remain active (even in dead people) until another object or person is seen.
B. Yes, but everything will be upside down because the eyes work by inverting what is seen.
C. No, because photoreceptors work by depolarizing and quickly return to their set point.
D. No, because any remaining image would be hard to tell apart from the opponent afterimage.

Answer 1

C. No, because photoreceptors work by depolarizing and quickly return to their set point.

Vision, like all the senses, works by creating action potentials in sensory neurons, specifically photoreceptors in the eye. These photoreceptors sense changes in light and dark (rods) and changes in color or wavelength (cones). Whenever a photoreceptor is stimulated enough it sends an action potential to a ganglion cell, optic nerves, the thalamus, and to the occipital lobe. This means the “image” isn’t an image at all, but an impulse sent through many nerves until it reaches the portion of the brain that can make “sense” of these impulses.
 
Right now we have the technology (fMRI) to make an educated guess about what a person is looking at or thinking about (e.g. animals, natural objects vs. man-made objects) but we cannot say with any certainty what the object was or whom the person was. In short, if we had the brain imaging technology the best bet would be to look inside the skull, not inside the eye.
 
Common misconceptions about vision include: vision works like a camera so any image seen will result in a tiny version of that object in the eye; vision works by shooting beams out of the eye (extramission).