

ARTICLES 

Year : 1983  Volume
: 31
 Issue : 5  Page : 528531 

Determination of the time of death by estimating potassium level in the cadaver vitreous humour
RL Agrawal, PC Gupta, S Bhasin, CK Nagar
Department of Ophthalmology, R.N.T. Medical College, Udaipur, India
Correspondence Address: R L Agrawal Department of Ophthalmology, R.N.T. Medical College, Udaipur India
Source of Support: None, Conflict of Interest: None
PMID: 6671749
How to cite this article: Agrawal R L, Gupta P C, Bhasin S, Nagar C K. Determination of the time of death by estimating potassium level in the cadaver vitreous humour. Indian J Ophthalmol 1983;31:52831 
How to cite this URL: Agrawal R L, Gupta P C, Bhasin S, Nagar C K. Determination of the time of death by estimating potassium level in the cadaver vitreous humour. Indian J Ophthalmol [serial online] 1983 [cited 2015 May 23];31:52831. Available from: http://www.ijo.in/text.asp?1983/31/5/528/29537 
One of the most important question at any forensic autopsy which until now has not been answered satisfactorily is the exact time of death.
Since the earlier attempts, failed to meet the definite postmortem interval, for variable reasons with much success, the postmortem biochemical changes in various body fluids (Blood, serum, cerebrospinal and intraocular fluids) have been tried for the estimation of time of death. Vitreous humour was preferred because it has a large volume, is easily obtainable, usually free from contamination and the changes in its biochemical parameters take place more gradually. Sturner^{ [1]} also remarked the frequent "Miraculous escape" of the eye even in the most severe cases of head injury and burns.
Following the pioneering work of Naumann^{ [2]} who estimated the levels of various substances in vitreous humour, Jaffe^{ [3]} first noted increase in vitreous potassium level in a regular fashion after death. This was later substantiated by various other workers^{ [1],[4],[5]}.
Materials and Methods   
Vitreous humour was aspirated from 99 eyes of 50 deceased, where exact time of death was known. In case of hospital deaths the cases, where electrolytes or diuretics were given prior to the death, were excluded from the study.
Syringes and rubber stoppered glass vials used for collecting the vitreous samples were washed with double distilled water and dried in hot air oven. 1.5 to 2.0 ml of vitreous was aspirated by slow and guarded suction from the centre of the eyeball by an 18 gauge needle through a puncture made 56 mm away from the limbus temporally. Water was replaced in the eye ball for cosmetic purpose.
In each case two samples were collected first from the right eye and second from the left eye after lapse of few hours depending upon the disposal of dead body. Potassium levels were estimated by flame photometer125 with digital meter mining unit (systronics) after appropriate dilutions (usually 100 times).
Observations   
The vitreous humour potassium concentration in 99 eyes of 50 deceased was estimated at known postmortem interval varying from 30 minutes to 35 hours.
Variation with age & sex:
No statistical significant variation in vitreous potassium concentration with age and sex was found at any time interval after death.
Variation in potassium concentration between two eyes when vitreous samples were aspirated simultaneously:
The potassium concentration in vitreous humour of the two eyes was found to be almost equal when vitreous samples, in 6 cases, were aspirated simultaneously from both eyes at various postmortem intervals.
Changes related to the time of death:
There was linear rise in vitreous potassium concentration to lengthening postmortem interval as revealed in [Figure  1]. It was also observed that the vitreous potassium values increased upto 24 hours after death and no significant rise was seen after that period, though this observation cannot be said to be authentic as we had only few cases recorded after 24 hours [Table  1].
Coefficient of correlation (r):
In order to demonstrate that there was clear relationship between postmortem interval and potassium concentration. Coefficient of correlation was calculated (r = 0.985). This indicates that there is almost perfect positive correlation between the postmortem interval and vitreous potassium concentration, so the postmortem interval can be calculated if vitreous potassium concentration is known.
Since both variables are chosen at random, the time of death can be estimated from the Regression equation:
X = X+bxy(YY) (1)
Where:
X = The estimated time of death in hours
X = 9.76 hours
Y = Potassium values in meq/lit. Y  9.13 meq/lit.
bxy  Coefficient of regression = 1.94 hours/meq/lit.
So by putting potassium concentration values in this equation we can estimate the time of death upto 24 hours, with standard error of L 2.26 hours in 95% of the cases and confidence limit of 3.39 hours.
From the value of regression coefficient bxy = 1.94, it appears that the I meq/lit. vitreous potassium concentration increases in 1.94 hours of postmortem inversal.
Changes within a pair of samples:
Average potassium concentration at zero postmortem interval i.e. at the time of death, was calculated and came out to be 3.94 meq/lit.
Potassium values in meq; lit plotted against time (in hours) for a typical pair of samples [Figure  1]. `A' indicates the calculated potassium value of 3.94 meq/lit at the known time of death. `B' indicates the determined value Y_{ 1} , of potassium at first sampling and `C' the value Y, of potassium at the second sampling. `A' is the intersection of the extension of line BC and the normal horizontal line from 3.94 meq/lit. level and indicates the estimated zero is the projection of BC on the horizontal line and gives the time interval (a) in hours between the 2 gives the time `X' elapsed from death to the first sampling and A'D gives the estimated time X'.
From the similarity of triangles A'BD and BCE we derive:
The estimated time, X' from equation No. 2 and the actual time after death, X are strongly correlated. The hypothesis of this new equation was checked by Chisquare test and came out to be correct and justified.
Discussion   
The normal concentration of potassium in vitreous humour of human being is 2.6 to 4.2 meq/lit. during life^{ [6]}. It is believed that during life, potassium enters into the vitreous humour through ciliary body which is demonstrated by Radioisotope technique, using the frozen segmentation method, which showed that the potassium concentration was highest in the anterior portion of the vitreous body^{ [7]}.
The linear relationship of increase in vitreous potassium concentration to lengthening postmortem interval is arithmetic rather than logarithmic, in this regards our results are in full agreement with the results of other workers^{ [1],[3],[4],[5]}.The autolysis of the vascular choroid and retinal cells is thought to be responsible for this rise^{ [2]}.
Few facts of present study are compared with 'chat of Sturner & Gantner^{ [3]}sub (1964) and Adjutantis and Coutselinis^{[5]} (1972) in [Table  2].
Coe^{ [5]} pointed out that confidence limit of this method for estimation of postmortem interval exceeded + 10 hours. This high standard error may be due to single sampling of vitreous humour. The averages of postmortem intervals and potassium concentrations were used in present study for calculating the time of death after taking two samples first from right eye and second from left eye, at an interval of few hours. This will decrease the error of individual variation and errors during aspiration and dilution of vitreous humour.
Few sources of errors can occur while aspirating the vitreous. These errors are technical in nature and can be avoided with due care. Firstly if vitreous aspirate is less than 0.5 ml, it may give unrepresentative result; owing to the uneven distribution of potassium within the vitreous body. Secondly, unduly forceful aspiration of the vitreous humour should be avoided because it can cause detachment of retinal cells and impart a cloudiness to the specimen.
Although it is doubtful that whether the precise time of an unwitnessed death can be determined in every instance by any one method, such are the promises of the vitreous potassium technique. It is a remarkably simple and accurate method for estimating the postmortem interval upto 24 hours. Further studies are warranted to unfold its full impact on the future practice of the Forensic Medicine.
Summary   
The vitreous humour potassium concentration in 99 eyes of 50 deceased was estimated by standard method of flame photometry at known postmortem interval varying from 12 hour to 35 hours. The results of this study reaffirm the arithmetic linear relationship of increase in vitreous potassium concentration to lengthening postmortem interval. The rate of rise of vitreous potassium concentration was 0.52 meq/lit/hour with the standard error of + 2.26 hours in 95% cases, upto 24 hours. It is remarkably simple and accurate method for estimating the postmortem interval as compared to other methods, where there was wide variation in timing.
References   
1.  Sturner, W.Q., & Gantner, G.E., Am. J. Clin.Pathol., 42, 137, 1964. 
2.  Naumann, H.N., Arch. Ophthalmol., 62, 356, 1959. 
3.  Jaffe, F.A., J. Forensi, Sci., 7, 231, 1962. 
4.  Coe, J.I., Am. J. Clin. Pathol., 51, 741, 1969. 
5.  Adjutantis, G., and Coutselinis, A., ForensicSci,, 155, 1972. 
6.  Davson, H., Physiology of the ocular and cereb rospinal fluids. London: J&A. Churchill, 1956. 
7.  Duke Elder & Goldsmith, A.J.B., Recent advances in Ophthalmology, 4th ed. London J&A, Churchill, 1951. 
[Figure  1]
[Table  1], [Table  2]
