The appearance of eyes changes after death primarily due to a decrease in intraocular pressure and other postmortem processes.
Decrease in Intraocular Pressure
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Loss of Blood Pressure: After death, blood circulation ceases, leading to a significant drop in arterial blood pressure. This directly results in a decrease in the intraocular pressure (the fluid pressure inside the eye).
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Sunken Appearance: The reduced pressure causes the eyeball to lose its firmness, resulting in a sunken appearance. The eyes may appear less full and the surrounding tissues may seem more prominent.
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Softer Feel: Palpating the eyes after death will reveal a distinct softness compared to the firmness of the eyes in a living person.
Other Postmortem Changes
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Corneal Clouding: The cornea, the clear front part of the eye, becomes cloudy soon after death due to dehydration. This clouding obscures the iris and pupil, contributing to the altered appearance.
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Tache Noire: If the eyelids are not fully closed after death, the exposed sclera (the white part of the eye) may dry out, leading to a brownish or blackish discoloration called tache noire. This is essentially a postmortem drying artifact.
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Pupil Dilation: While pupils can be fixed and dilated or constricted depending on circumstances surrounding the death (e.g., drug use, lighting conditions), they often tend to dilate postmortem due to the relaxation of the muscles that control pupil size.
In summary, the combined effects of decreased intraocular pressure, corneal clouding, and potential drying artifacts result in the noticeable changes in the appearance of eyes after death.
