The human eye undergoes a series of transformations following death. Understanding these post-mortem changes involves examining both immediate physical alterations and the progressive decomposition that occurs over time. This exploration delves into the scientific realities of how the eyes change after life ceases.
Immediate Ocular Changes After Death
Immediately after death, the eyes exhibit several rapid and observable alterations. The cessation of brain activity leads to the loss of physiological functions, including eye movement and reflexes. The pupillary light reflex becomes absent within moments of death. The pupils often dilate due to the relaxation of the iris muscles, though they may later constrict with the onset of rigor mortis.
Within minutes to a few hours, the cornea begins to show signs of clouding. This loss of transparency is primarily due to the lack of oxygen and metabolic activity, which are necessary to maintain corneal hydration and clarity. The eye also loses its intraocular pressure, becoming flaccid, and the blood vessels in the retina may show “trucking” or segmentation.
Progressive Post-Mortem Eye Alterations
As time progresses, the eyes continue to undergo more advanced alterations. The initial corneal clouding intensifies, making the cornea increasingly opaque and potentially wrinkled. This progressive opacification can obscure the view of the deeper structures of the eye.
If the eyelids remain open, “tache noire” (black spot of the sclera) forms. This reddish-brown to brownish-black discoloration appears on the sclera where it is exposed to the air. It forms within three hours if the eyes are open due to drying and desiccation of the ocular surface. Internally, the vitreous humor undergoes liquefaction, changing from a gel to a more fluid consistency, and the retina can also show changes, such as folding, and the breakdown of blood vessels can lead to a marbled appearance.
Factors Influencing Ocular Decomposition
The rate and specific presentation of post-mortem eye changes can vary significantly due to several influencing factors. Environmental temperature plays a substantial role; colder temperatures slow down decomposition processes, while warmer temperatures accelerate them. Humidity also impacts the rate of drying, with arid conditions leading to faster desiccation of the ocular surface and quicker development of changes like tache noire.
Whether the eyelids are open or closed is an important factor. If the eyelids remain open, the eyes are exposed to air, leading to more rapid drying and the earlier appearance of corneal clouding and tache noire. Conversely, if the eyelids are closed, these changes are delayed, and certain causes of death or pre-existing medical conditions can influence the speed and nature of ocular decomposition.
Common Misconceptions About Post-Mortem Eyes
Many popular beliefs about eyes after death are not supported by scientific understanding. A common misconception is the idea that the eyes “record” the last image seen before death. This concept, known as optography, involved attempts to photograph retinas to reveal a deceased person’s last sight. However, the retina ceases to function once the blood supply stops, and the visual pigments break down, making the retention of a discernible “last image” impossible.
Another belief is that eyes always remain open after death. While eyes can certainly be open, the muscles controlling the eyelids relax after death, which can allow them to close. If they remain open, it is often due to the position of the body, the natural relaxation of muscles, or the onset of rigor mortis in the facial muscles. Funeral professionals often manually close the eyelids for presentation purposes. The appearance and condition of post-mortem eyes are solely due to biological processes and environmental influences, not reflecting any conscious experience or emotional state at the time of passing.