The Bizarre Phenomenon That Happens To Human Eyes After Death

The main physical change that most of us are aware of happening after death is rigor mortis, where the body stiffens due to the lack of oxygen in the cells. There are other known post mortem changes, however, that can happen post mortem, and one of them, known as tache noir, specifically affects the eyes. As well as being an indicator of death (usually), it can also help to provide an estimate on how long it has been since a person took their last breath.

Tache noire de la sclerotique (often shortened to tache noir) literally translates as "black spot of the sclera" and refers to a dark line going through the white of the eye. It happens almost exclusively after death, though in some very rare cases it has happened in living patients.  The effect tends to happen to people who die with their eyes open, as the eyes begin to dry out on exposure to the air. The location of the horizontal line can vary, depending on the position of the eyelids, and can be a dark red-orange color, or completely black.

While living, there are various processes that the body carries out spontaneously that are helping to keep our eyes moist and functioning. Every time you blink, you are keeping moisture in your eyes by spreading tears across them, and creating oil in the meibomian glands.  Though it happens involuntarily, we blink up to 28,000 times every day! Producing tears, whether through emotional or physical stimulation, also hydrates the eyes and prevents vision problems and physical discomfort.

After death, when blinking ceases and no more water is taken in, the eyes can dry out very quickly. Like in sleep, closed eyelids can protect the eyes from the air reasonably well, but eyes which remain open post mortem are likely to dry out very quickly. Because tache noir is part of the decomposition process, and can appear within a few hours of death, it can be used as a rough indication for time of death. However, this can be influenced by the temperature, humidity, and weather, and if the body was found indoors or outside. While tache noir may seem like a strange, eerie process, it is simply a natural part of the decomposition process on corpses where the eyes remain open after death.