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| ARTICLE |
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| Year : 1983 | Volume
: 31
| Issue : 5 | Page : 635-638 |
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Glucose-Estimation in tear fluid-Its diagnostic significance-a preliminary study
RK Mediratia, JN Rohatgi
Department of Eye, Patna Medical College, Patna, India
Correspondence Address:
R K Mediratia
Department of Eye, Patna Medical College, Patna
India
 Source of Support: None, Conflict of Interest: None  | Check |
PMID: 6671780 
How to cite this article:
Mediratia R K, Rohatgi J N. Glucose-Estimation in tear fluid-Its diagnostic significance-a preliminary study. Indian J Ophthalmol 1983;31:635-8 |
Of the diffusable non-ionised substances in the tear fluid, greater interest has been focussed on glucose and different workers have assigned different values to its concentration in the tear. This is partly due to the different methods of estimation.
The methods (for the estimating glucose in tear fluid) are both quantiative and qualitative.
For the qualitative tests-a commercial preparation clinistix (Amesco) has been used to detect glycosurea and to estimate blood sugar level as also tear glucose in diabetics (Lewis, 1957).
Clinistix paper test strip is applied to the lower conjunctival cul-de-sac-for ten seconds to moisten the end of the paper test strip or alternatively, a strip moistened with water is applied for a few minutes. The results should be read after a minute though any colour change would be noticeable within thirty seconds. If glucose is present-a blue colour will develop. The depth of the colour is roughly related to the blood sugar level.
Instead of applying clinistix strip to the lower conjunctival cul-de-sac, Schirmer-test strips could be placed in the lower conjunctival sac and kept there for a few minutes till they are wet. And against, this wet strip, clinitix paper strip is placed for a minute and depending on the amount of glucose present, the colour in the clinistic strip developes from light blue to dark brown. It has been found that tearglucose concentration less than 10 mgm./100 ml. produces no colour change in the clinistix.
Concentration above 22 mgm. /100 ml. gave a dark blue colour; light and medium blue were produced by glucose concentration of 10 to 17 mgm./100 ml.
The quantiative analysis was done on the tear fluid collected in a standard capillary tubethe amount being 13 microlitre. Thereafter, the chemical reaction was as follows:
Glucose (Glucose/Oxidase) Gluconic acid + Hydrogen
peroxide.
Hydroden Peroxide + reduced O-dianisidine
Peroxide H 2 O + Oxidised
O-dianisidine.
Oxidised O-dianisidine + Sulphuric acid
-Red chromatophore
The reading being done by Unimeter.
| Observations | |  |
Thirty (30) normal individuals, with healthy eyes had their-tear fluid analysed for glucose by the quantiative method. In them, the range of glucose varied from 2 to 6 mgm./100 ml. It was, however, slightly different for the different age-group of the individual as given in the table below:[Table - 1]
In thirty (30) cases of acute mucopurulent conjunctivitis, the average glucose value in tear fluid was found to be as follows:
1.57 mgm./100 ml. in the age group of 0 to 20 years. 2.25 mgm./100 ml. in the age group of 21 to 30 years and 2 mgm./100 ml. in the age group of 31 to 40 years.
The figures are, thus, on the lower side when compared to the average value of glucose
in normal tear fluid.
While one could not be dogmatic it is possible to explain the lower value of glucose in acute mucopurulent conjunctivitis, due to its increased utilisation (of glucose) by the bacteria and conjunctival tissue. One could also suggest that in infections due to mixed bacterial flora the utilisation of glucose is higher as compared to the infections caused by single bacterial flora.
The glucose value of tear-fluid in cases of allergic conjunctivitis was also determined as given in the table. This was found to lie in the range of 3.50 to 4.5 mgm/100 ml. taking the average of all age groups. The normal average as mentioned above was between 3.42 mgm/100 ml. to 4.69 mgm./1.00 ml. Thus, the difference between the two ranges lies between 0.08 ml, to 0.19 mgm/100 ml. and this is too small to be of any practical significance.
Similarly the glucose level in tear fluid of chronic conjunctivitis cases was significantly decreased when compared to the normal value. The explanation could be the same as in case of acute conjunctivitis that in bacterial infection glucose is utilised by the invading bacteria for their development and growth.
Based on the same explanation of increased glucose utilisation by the invading bacteria, one could explain the decreased value of tear glucose in the ten cases of corneal ulcer (the range between 1.87 to 3.34 mgm./100 mg.). In Xerophthalmia cases, however, the decrease in tear glucose level compared to the normal value was for practical purpose insignificant (0.21 mgm/ 100 ml.).
In a series of ten (10) normal individuals, blood sugar and tear glucose under fasting condition was analysed both by the routine quantiative methods as well as by Diastic paper reading. The findings are given below in the table.
It would be seen that with fasting blood sugar varying from 78 to 107 mgm/ 100 ml., the tear glucose varied from 3 to 5 mgm/100 ml. and this did not produce any change in the reagent area of the clinistix paper strip in these non-diabetic patients.
In another ten (10) well established diabetic cases-fasting blood sugar and fasting tear glucose was analysed as well as Diastix reading was taken using clinistix paper strip and the finding are shown in the table.[Table - 2]
These patients were cases of uncontrolled diabetes attending diabetic-clinics. While the blood sugar ranged from 158 to 310 ml./100 ml. the tear glucose was from 12 to 24 mgm/ 100 ml. and this produced colour change in the clinistix paper strip. It was, noted, however, that the rise of the blood sugar and tear glucose level are not proportionate.
| Conclusion | | |
It was observed that the rise in glucose level in tear fluid is much higher than the blood glucose rise amongst the decompensated diabetes.
With this preliminary observation, it is rather difficult to assign a cause for this disproportionate rise between blood sugar and tear glucose level.
The diastix reading observation forms a significant method for routine check up of diabetic patients. In Eye Clinics, diabetic patients could be screened out quickly and without much trouble to them as compared to collecting samples of urine and blood sugar. Further the semi-qualitative nature of this could help in assessing the degree of control of diabetes[5].
| References | | |
| 1. | Lewis, J.G., Brit. Med. Journal, Vol. I, 585, 1957.  |
| 2. | Lewis, J.G. & Stephens, P.J., Brit. J. Ophth., 42, 754, 1958. |
| 3. | Giardini, A., Roberts JRE, Brit. J. Oneth., 34: 737, 1950. |
| 4. | Antonio, R. Gasset, Lewis et al, Amer. J. Okhth., 65: 414, 1968. |
| 5. | Adler, H.F., Physiology of the Eye, 6th Edition, C.Y. Mosby Co. London, Page 20, 1975. |
[Table - 1], [Table - 2]
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