The color of a person’s eyes does not fundamentally change in terms of the pigment itself, but the eye undergoes several physical alterations that can significantly affect its appearance. These post-mortem changes can lead to an illusion of color variation, often making the eyes appear dull, cloudy, or even a different shade.
The Science of Eye Color
Eye color in living individuals is primarily determined by melanin, a pigment also responsible for skin and hair color. The amount and distribution of melanin within the iris, the colored part of the eye, dictate its hue. Two main types of melanin contribute to eye color: eumelanin, which produces brown and black shades, and pheomelanin, which creates red and yellow hues.
Brown eyes have the highest concentration of melanin, absorbing most light and resulting in a dark appearance. Blue eyes, conversely, have very low melanin content in the front layers of the iris. Their blue appearance comes from how light scatters within the iris’s stroma, a phenomenon known as Rayleigh scattering. Green eyes result from a moderate amount of melanin, often a combination of both eumelanin and pheomelanin, alongside light scattering effects.
Post-Mortem Eye Appearance
After death, the eyes undergo various physical changes that alter their appearance. One of the earliest and most noticeable changes is corneal clouding, also known as corneal opacity. This haziness typically begins within two hours if the eyes are open, becoming progressively more opaque over the next day or two. This clouding occurs because the endothelial cells in the cornea, which normally pump water out to maintain transparency, cease to function due to lack of energy, causing water to accumulate and disrupt the collagen fibers.
Another significant change is the loss of intraocular pressure, the fluid pressure inside the eyeball. This pressure decreases dramatically after death, causing the eyeball to become flaccid and appear sunken. This reduction in pressure contributes to the overall altered look of the eye.
Furthermore, if the eyes remain open after death, a phenomenon called “tache noire de la sclérotique” can develop. This involves the formation of brownish-black discolorations on the exposed sclera (the white part of the eye) between the eyelids. These structural and superficial changes, rather than a change in the iris’s pigment, are responsible for the altered appearance of the eyes post-mortem.
Common Misconceptions
The belief that eyes change color after death often stems from misinterpreting the physical changes that occur. The clouding of the cornea, the dulling of the eye’s surface, and the sunken appearance can make the iris seem less vibrant or even a different shade, such as a milky gray or blue. This visual alteration is not due to a shift in the melanin pigment, which remains stable, but rather to the loss of transparency and structural integrity of the surrounding ocular tissues. However, the underlying genetic programming for eye color, dictated by melanin levels in the iris, does not cease or reverse upon death. The “color change” is an optical effect caused by post-mortem processes affecting the eye’s clarity and form.