Can the eyes of the deceased really keep the figure before their death? Why did the forensic doctor look into the eyes of the deceased during the autopsy?

There have been rumors that the last image will be left in the eyes of the deceased, so forensic experts will extract this image as the basis for finding the murderer, and the resulting destruction of the body is simply outrageous! So is the truth really as rumored?

Can the human eye leave the last image it sees?

The camera can focus the beauty of nature or people on the film through a precise optical lens to leave an image! The human eye is the most sophisticated camera system, and of course it can leave the final image in the fundus! But in fact, this is a complete misunderstanding of the camera and the human eye system!

Why can a camera leave a lens? Let's take a film machine that uses film as an example. Its negative is silver halide coated on polyacrylate substrate. When the light focused by the lens shines on the silver halide, the silver halide will change into different shades of black silver according to the different irradiation time, and it will be fixed on the base after the development process. This is a common black and white negative!

Color films are three layers of silver halide to represent the three primary colors, and there are also films that have been imaged, such as Polaroid. It won't take long to press the shutter to spit out a color photo!

Modern digital cameras use photoelectric coupling elements or metal oxide semiconductors instead of negatives, but what they get is electrical signals, which are encoded by image processor algorithms and stored in the camera's memory card. If you want to display it, you can read this stored file and restore it to a picture on the display screen, which is the photo we have seen! If you take many photos every second and connect them, it will become a moving picture, which is the basic principle of the camera!

Does the human eye have this recording and storage function?

From negative film to CCD of digital camera, although the final result is similar, the realization method is different. What CCD gets is electrical signal conversion, while digital camera is chemical change! So what is the principle of seeing things with the naked eye?

Naked eye structure

The picture above shows the structure of human eyes. The light focused by the cornea and the lens is on the retina of the fundus, converted by the electric signal of the retina, guided to the image processing unit of the brain through the optic nerve, and forms a stereoscopic picture through the visual difference between the left and right eyes. Under normal circumstances, the human brain can judge the size and distance of an object through the stereoscopic vision of both eyes!

Stereo vision is very important for the birth of human civilization. Although it lacks an all-round perspective, for example, birds have almost a 360-degree perspective, but they have no stereoscopic vision, and there is a blind spot in front of their heads at close range! Although humans lack vision of the rear, this can be achieved by turning their heads.

A chameleon with a 360-degree view.

The naked eye has no function similar to negative film.

Common negatives need to be treated with developer before the chemical changes on the negatives can be fixed and become the negatives we see, otherwise we will continue to wait for photochemical changes! The photosensitive organ of the human eye is the retina, which consists of three kinds of two kinds of photosensitive cells, rod cells and cone cells. The objects targeted by these two cells are slightly different. Rod cells are mainly sensitive to light and shade, and cone cells are mainly sensitive to color!

Among cones, L cones are called red receptors for short. In fact, they are most sensitive to green and yellow. At the wavelength of 560 nm, S cone cells and M cone cells correspond to blue and green, but not the standard blue and green. For example, M cone cells are most sensitive to light at 530 nm, while S cone cells are most sensitive to light at 420 nm!

Visible light wavelength distribution

Therefore, the naked eye is not the standard RGB color, and the structure of the eye cannot be imaged directly, because the rod cells and cone cells convert the obtained light into electrical signals, which are sent to the brain for image processing through the optic nerve, and the optic nerve cannot store information. So we can see that the colorful world is supplemented by the brain, and the brain also has super-realistic enhancement functions, such as imagining unknown objects seen at night as monsters.

To put it simply, the fundus retina only converts signals, and no image remains, so it is impossible to extract images from the eyes of the deceased, unless there is the possibility that the fundus is burned by super light, such as laser pens (commonly used pointer laser pens and pointer pens). This kind of laser pointer with several hundred milliwatts power is very harmful, which can directly burn the retina, and the damage is irreversible.

Why did the medical examiner examine the victim's eyes?

It is often seen that the protagonist with halo in war drama opens his eyes to see if the pupil is dilated and the reflection of light disappears to judge whether his companion is dead, because the sphincter of pupil is dominated by the third cranial nerve: oculomotor nerve, and the dilated pupil indicates that the reflection of cranial nerve disappears, which is one of the signs of brain death and the only one!

But in the forensic identification stage, death is beyond doubt, so why should forensic doctors observe their eyes? This has the following points:

Victims who suffocate will have bleeding spots at the eyeball-eyelid junction in the eyelid.

The left and right pupils caused by all kinds of damaged and dead pupils are different in size, small in circle and inconsistent in eyes. Pupil enlargement is not the only criterion, because poisoning may shrink the pupils.

The opacity of eyeball cornea can roughly determine the time of death, so it is best to perform corneal transplantation within a few hours after the death of the donor. If it is turbid for a long time, it is no longer suitable for transplantation.

Therefore, looking at the eyes in forensic identification is not to confirm whether it has left a final impact, but this process is very important, because some information it shows is of great help to forensic doctors. Of course, this is also an auxiliary means. The real identification results need other means to confirm, but it does not hinder the eyes, a relatively simple method!