Year : 1970 | Volume
: 18 | Issue : 4 | Page : 162--166
Evaluation of water drinking test and tonography in detection of glaucoma
Glaucoma Clinic Ophthalmic Department, Government Erskine Hospital, Madurai-13, India
Glaucoma Clinic Ophthalmic Department, Government Erskine Hospital, Madurai-13
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Sivaramasubramanian P. Evaluation of water drinking test and tonography in detection of glaucoma.Indian J Ophthalmol 1970;18:162-166
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Sivaramasubramanian P. Evaluation of water drinking test and tonography in detection of glaucoma. Indian J Ophthalmol [serial online] 1970 [cited 2022 Nov 26 ];18:162-166
Available from: https://www.ijo.in/text.asp?1970/18/4/162/35633
The earliest method of detection of glaucoma is by screening all patients by tonometry. In some cases, which show a border line intraocular pressure, it is essential to do provocative tests and thereby detect further the evidence of glaucoma. Of all the provocative tests for open angle glaucoma, the simplest, the cheapest and easiest is the water drinking test. Sometimes it is not surprising to find negative results even with this test since it depends upon a number of features, like the mobility of gastro-intestinal tract, the rapidity of intake of water and the degree of homodilution. If these cases are followed by tonography a still further number of glaucoma cases can be uncovered.
To study the efficacy of any provocative test, it should be studied both in obvious glaucoma cases and in normal subjects. Then a comparative merit of these cases can be drawn.
Method of Study
All the patients over the age of 40 that came to our Eye Department were subjected to tonometric study. In this method both eyes were anaesthetised with two per cent anethaine and tonometric reading was taken in each eye twice in quick succession. He was asked to look at the ceiling and without exerting pressure by the finger on the globe the readings were taken. Cases with obvious infection and ulcers were excluded from the series.
These patients were grouped into three different categories
Category (i) : Persons with an intraocular pressure below 2o.6 mm.
Category (ii) : Persons with an intraocular pressure between 2o.6 and 25.8 - "Glaucoma suspects".
Category (iii) : Persons with an intraocular pressure over 25.8 mm. Schiotz or the so-called glaucoma patients.
Since the intra-ocular pressure between the two eyes of a person may vary, the study was conducted with respect to the number of eyes rather than on the number of individuals.
These patients were subjected to water drinking test by giving one litre of water on an empty stomach within 5 minutes. Then the intra-ocular prescure was recorded for every fifteen minutes for one hour. This was followed by tonography by a Schiotz's weighted tonometer by keeping it on the cornea for 4 minutes, since the electric tonometer was not available in this Institution. The coefficient of aqueous outflow is determined by making use of table prepared by the American Academy of Ophthalmology. The P O/C ratio is also determined from the above values.
Material of Study
Water-drinking test tonography was carried on cases of all the three categories mentioned above:
Category 1 - 127 eyes.
Category 2 - 88 eyes.
Category 3 - tog eyes.
Total - 324 eyes.
Normal eyes were subjected to the test for the following reasons
1) One eye with obvious or suspected glaucoma and the other eye normal.
2) Myopic eyes with a myopia of more than 6 D.
3) To have a controlled study of the results.
4) When the difference of intraocular pressure between the two eyes was more than 4 mm (Downey's sign).
Results of the Study
I. Results of Water Drinking Test
A. In 127 eyes with normal intrapressure [Category (i)][Table 1]
B. Results of water drinking test in 88 eyes of glaucoma suspect [Category (ii)][Table 2]
C. Water drinking test in log eyes of glaucoma [Category (iii)][Table 3]
II. Results of Tonography following Water Drinking Test:
A. Water drinking test tonography was done in iz7 eyes with normal intra-ocular pressure.
Al. 6 eyes showed a rise of tension of over lo mm. of Hg. C value in the above 6 eyes was below o.15.[Table 4]
B. In 88 eyes of glaucoma suspects, tonography was conducted. They were classified under the following headings:[Table 5]
C. 109 eyes with an intra-ocular pressure over 25.8 were subjected to water drinking test tonography 37 cases showed increase of intraocular pressure of more than lo mm. following water drinking test 10 cases showed a rise of 8-10 mm.
The rest of the 62 cases showed only a rise of less than 8 mm. They were subjected to tonography and the results were as follows[Table 6]
Since sometimes the `C' value may not indicate the actual evidence of glaucoma, P O/C was determined to find out early glaucoma in cases having a `C' value of more than 0.15.
Analysis of Results:[Table 7]
Water drinking test by itself is positive only in about 33.7% of the cases. Further, it depends on the state of gastro-intestinal tract and the osmotic hypotony of blood serum that is achieved. Hence by this test alone all cases of glaucoma cannot be detected. Grant,, has suggested that if the test is followed by tonography the positive results reach upto 66%. Becker  suggests that if P O/C value is calculated and if the value is over 100 it can be considered as glaucoma. Hence, the detection of early cases rise to 94%.
We studied this series by doing the water drinking test and recorded the rise of intra-ocular pressure every 15 minutes. If the pressure rise was over 1o mm. it was considered as pathological evidence of glaucoma. We followed this test by tonography and considered all eyes in which the rise was less than lo mm. but tonography value was below o.15 as evidence of glaucoma. In the other groups having value of `C' between .15 to 2 the P O/C was calculated. If P O/C was over 100, these were also included as early cases of glaucoma.
This procedure was adopted in 127 normal eyes, in 88 eyes considered as glaucoma suspects since the intraocular pressure was between 20.4 to z5.8 and in 1o9 eyes of obvious glaucoma so that the results could be compared.
In glaucomatous eyes 33.9% of cases showed a positive water drinking test. `C' value was found less than 0.15, in another 44.9% and P O/C over 100 in 21.2% cases. This proved that if water drinking test is followed by tonography and P O/C value is calculated, it gives complete evidence for glaucoma.
In glaucoma suspects with an intraocular tension between 29.4 to 25.S water drinking test alone was positive in 22.7%. `C' value less than 0.15 in 17% and P O/C over 100 in 25%. Thus a total of 64.7% were proved to have glaucoma.
In normal eyes with the intraocular tension below 20.4, water drinking test was positive only in 4.7%, `C' value less than 0.15 in 18.9% cases and P O/C over 100 in 2.4%. Thus a total of 26% of cases of glaucoma were detected.
In all open angle glaucoma cases the method of studying P O/C following water drinking test gives 100% results as proof of glaucoma.
In patients with intra-ocular pressure between 20.6 to 25.8 the evidence of glaucoma is found in 64.7% of cases showing that this group of patients should be intensively studied for evidence of glaucoma.
These also show that in a random sample, the evidence of glaucoma in patients with normal intra-ocular pressure is z6%. This does not include all the patients who have attended the eye department, since some of them had acute infections in the external eye. This study also does not take into account those of the normal patients who had no complaints and hence have not attended the eye department. But this definitely indicates that the incidence of glaucoma is more than that in western countries, where its incidence is about 4%.
My thanks are due to Mohamed Meeran, the Tonometrist of the Clinic, for the data collected. I wish to thank the clerical staff for the help in bringing out this paper.
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|2||Becker and Friedenwald, J. S.: Clinical aqueous outflow, Arch. Ophth. 50 : 557, 1953|
|3||Clark, W. B. (editor) : Symposium on glaucoma. St. Louis, 1959. The C. V. Mosby Co.|
|4||Grant, W. M.: Tonographic method for measuring the facility and rate of aqueous flow in human eyes. Arch. Ophth., 4: 204, 1950.|
|5||Grant, W. M.: Clinical measurements of aqueous outflow. Arch. Ophrh.. 46 : 113, 1951.|
|6||Kronfeld, P. C.: Tonography symposium Tr. Am. Acad. Ophth., 65 : 133, 1961.|
|7||Newell, F. W. (editor) : Glaucoma: Transactions of the First, Second, Third, Fourth and Fifth Conferences, New York, 1956-1960, Josiah Macy. Jr. Foundation.|
|8||Weekers R. (editor) : Glaucoma symposium. Docum. Oph. 13 : (1959).|