Sanjukta Jana, B.Optom
Intern Optometrist, LVPEI, Bhubaneshwar, India
Post-mortem examination of a dead body is undertaken to determine the cause, manner, and time of death. It may also be useful for forensic case analysis. These examinations also have pathological significance. Post-mortem can be carried out by coroners but mostly by doctors. Usually carried out within 2-3 working days of a person’s death. (1)
Figure 1: Anatomy Of Vitreous And Ocular Barriers
Role of body fluids in autopsy
Body fluids suitable for analysis of death are – vitreous, cerebrospinal fluid, pericardial and synovial fluids. Blood is not used for post-mortem examination as there is degeneration of RBC and WBCs.
Advantage of vitreous over other body fluids in autopsy
The vitreous body is a colourless, transparent gel consisting of salts, soluble proteins, and hyaluronic acid contained within a meshwork of collagen. (2)
- Vitreous is easier to obtain.
- Vitreous is in a comparatively isolated position. Blood-vitreous or vitreoretinal barriers are functional terms describing the inability of the vitreous constituents to equilibrate with blood and with surrounding fluids. This makes it less affected by post-mortem contamination and putrefaction. (2)
- Despite having no blood vessels, the vitreous is metabolically active.
Post-mortem analyses of vitreous fluid
| Glucose and lactate | Diagnosis of death from diabetic coma with severely increased blood glucose level often becomes difficult as there are no obvious findings because of degradation of RBCs. In such cases, vitreous fluid can be examined. (2) |
| Potassium | Forensic scientists have evaluated the rise in potassium to investigate the death timing. After death, a rise in potassium levels in vitreous is seen due to leakage from surrounding cells in the retina and choroid because of active membrane loss. (3) |
| Oxygen and carbon dioxide | In fatal asphyxia where no forensic traces can be tracked partial pressure of oxygen and carbon dioxide in isolated vitreous is a way of investigation. Post-mortem gas analyses in blood give erroneous results due to contact of blood vessels with air within the gastrointestinal system. (3) |
| Sodium and chloride | Sodium and chloride content determines the volume of extracellular fluid. Hence, extreme sodium and chloride imbalances may result in fatality. While forensic investigations may reveal confirmation about water or salt intoxication, drowning, or beer potomania. Analysis of sodium and chloride ions generates erratic results hence vitreous examination is beneficial. (4) |
Role of Vitreous Humor in pathological diagnosis and cortical brain tissue
By examining vitreous levels in post-mortem levels of neurodegeneration biomarkers associated with Alzheimer’s Disease, Chronic Traumatic Encephalopathy (CTE). Post-examination studies revealed amyloid-beta, Phosphorylated tau, neurofilament light chain, and eotaxin-1. These biomarkers are associated with the pathophysiology of cortical brain disorders. (5)
Optometric Influence On Post-Mortem- Are You Wondering What Optometry Has To Do With Post-Mortem Investigation?
Forensic evaluation of vitreous will show erroneous results until and unless certain optometry facts are kept in mind.
- Sodium concentration is slightly lower in blood than in vitreous humour.
- Cause of death has an influence on post-mortem potassium concentrations.
- Chloride levels are slightly higher in vitreous fluid than in blood.
- Glucose, as well as Calcium levels, are lower in vitreous fluid than in blood.
- Vitreous glucose levels decrease consistently to a limited extent, in the early phase after death. Even after death, the glucose keeps being consumed by surviving vitreous and retinal cells in the vitreous, hence causing. When the organism is dead and no oxygen is available, the living cells switch on to an anaerobic mode of glycolysis, resulting in transformation of glucose to lactate.
Hello, future detective, now you are ready to be the next Sherlock Holmes. The ways vitreous may be useful in detecting crimes is a topic of debate and I welcome optometrists to actively participate in this discussion.
References
- https://www.nhs.uk/conditions/post-mortem/#:~:text=Post%2Dmortems%20provide%20useful%20information,effective%20treatment%20in%20the%20future
- Zilg B, Alkass K, Berg S, Druid H. Postmortem identification of hyperglycemia. Forensic science international. 2009 Mar 10;185(1-3):89-95.
- Zilg B, Bernard S, Alkass K, Berg S, Druid H. A new model for the estimation of time of death from vitreous potassium levels corrected for age and temperature. Forensic science international. 2015 Sep 1;254:158-66.
- Zilg B, Alkass K, Berg S, Druid H. Interpretation of postmortem vitreous concentrations of sodium and chloride. Forensic science international. 2016 Jun 1;263:107-13.
- Wright LM, Stein TD, Jun G, Chung J, McConnell K, Fiorello M, Siegel N, Ness S, Xia W, Turner KL, Subramanian ML. Association of cognitive function with amyloid-β and tau proteins in the vitreous humor. Journal of Alzheimer’s Disease. 2019 Jan 1;68(4):1429-38.
Figure References- Figure 1-Sebag J. The vitreous. Structure, function, and pathobiology: Springer Verlag.
Vitreous is one of the important body fluids which plays important role for Vision (based on Refractive index) as well as ruling out few important abnormalities of bodies (based on biopsy). In case of Ketoacidosis (increased Ketone bodies in blood due to chronic Diabetic and chronic Alcoholism) and Hypothermia(Causes of death due to prolonged cold exposure), Vitreous analysis will play major role.