WARNING: This post includes a graphic image.
Tiah asked: “Is there much the eyes can tell us about cause of death, other than the obvious of petechiae?”
Excellent question, Tiah! First, as a refresher, keep in mind that generally visible decomposition changes in the eyes are of minimal value regarding establishing post-mortem interval. And, in answer to your specific question, visible decomposition changes are of almost no value (trauma is an exception) regarding establishing cause and manner of death. You are of course correct about petechial (capillary) hemorrhages (also called petechiae), which can be the result of a variety of causes. Perhaps we can discuss petechiae in a later post. Again, despite what is sometimes depicted on television or in movies, the presence of petechiae will not result in a forensic pathologist immediately jumping to the conclusion that asphyxia was the cause of death.
To elaborate a bit, post-mortem changes such as softening of the eyes after death is due to vitreous fluid evaporation and protein degeneration. An analogy (albeit perhaps a bit disturbing to think about) would be that of a grape, which after extreme drying becomes a raisin. Very generally speaking, clouding of the cornea and drying of the conjunctiva results in a yellow or brown or yellow/brown discoloration. Oddly, the conjunctiva has sometimes been subsequently noted as becoming dark blue — due to infiltration by choroidal pigment, but that phenomenon is less obvious if the eyes are closed. Note: the choroid is the pigmented middle layer of the eyeball which provides oxygen and nourishment to the outer layers of the retina.
Many times, the observation and documentation of pupil size is what we call a “negative pertinent”, something that we take note of; an observation of some aspect of the decedent that would be expected. Not documenting such things may suggest in a court of law, that “no attention was given to it”. Not documenting various negative pertinents also suggests there is no possibility of forensic interpretation sometime in the future (due to a positive scientific advancement). Thus, a forensic pathologist or medical-legal death investigator will often document pupil size, i.e. right pupil 3 mm, left pupil 6 mm. Yet, getting back to your question, the actual size of the pupils after death is thought to be diagnostically valueless. Interestingly, an exception was found back in the 1950’s when organic phosphorus insecticides become available and were being used in homes, farms and gardens. The medical community was alerted and aware of to the poisoning potential, as were medical examiners. Although personally I’ve never seen it, I’ve heard described the diagnostic exception of miosis (constriction of the pupil of the eye — to less than or equal to two millimeters) allegedly resulting from death due to ingestion of organic phosphorus insecticides.
Focusing upon the area around the eyes (rather than the eyes themselves), one frequently recognized trauma based transformative feature typically associated with basal fractures, is that of “raccoon eyes” or “spectacle hemorrhages”. In severe trauma such as a skull fracture from ballistic trauma, tears in the membranes surrounding the brain may often results in seepage into the soft tissue around the eyes. As such, this phenomenon, which presents at examination, does have diagnostic value.
I hope this was somewhat helpful.
Best regards, -Hal