|Year : 1971 | Volume
| Issue : 2 | Page : 85-90
Average distribution of intraocular pressure in Indians by applanation tonometer
SP Gupta, P Mehta
Dept. of Ophthalmology, King George's Hospital, Lucknow. U. P., India
S P Gupta
Dept. of Ophthalmology, King George's Hospital, Lucknow. U. P.
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gupta S P, Mehta P. Average distribution of intraocular pressure in Indians by applanation tonometer. Indian J Ophthalmol 1971;19:85-90
|How to cite this URL:|
Gupta S P, Mehta P. Average distribution of intraocular pressure in Indians by applanation tonometer. Indian J Ophthalmol [serial online] 1971 [cited 2020 Apr 10];19:85-90. Available from: http://www.ijo.in/text.asp?1971/19/2/85/34984
As our efforts to improve the understanding and management of glaucoma grow more purposeful and systematic, the measurement of normal intraocular pressure becomes of special importance, since a large variety of clinical predictions are based on it.
Furthermore with the advent of tonography and the possibility of investigating intraocular fluid dynamics in man, the reliability of the absolute value of the intra-ocular pressure has assumed added importance. With a view to find out the average normal value of intra-ocular pressure, the present study was carried out, because little information is available in the literature regarding the distribution of applanation pressure readings in the Indian population.
| Material and Methods|| |
The sample consisted of 300 normal individuals of Indian origin mostly belonging to Uttar Pradesh. In order to have normal eyes as far as possible the subjects had to fulfill the following conditions:
(1) Age of 20 years or more.
(2) Absence of ocular complaints with or without an error of refraction, improvable to 6/6 and J(1) with glasses.
(3) Absence of an eye condition requiring active treatment.
(4) No history of ocular trauma or surgery.
A short ophthalmic history with special stress on family history of glaucoma was taken from each individual.
The following examinations were done:
(1) External eye examination in detail.
(2) Fundus examination in detail.
(3) Slit-lamp examination of anterior segment in detail.
Applanation tonometry was performed by means of Goldmann's Applanation Tonometer mounted on the Hagg-Streit Slitlamp 900, with the well-known technique after a surface anaesthetic and fluorescein (0.25%) drop.
The intra-ocular pressure of the right eye was always measured first and three consecutive readings were taken of each eye and their mean was taken to be the final reading.
If the intra-ocular pressure was more than 21 mm. Hg. the eye was subjected to further tests for glaucoma.
| Observations and Results|| |
The distribution of males and females in the entire sample according to age group was as shown in [Table - 1].
Males consisted of 58.6% of the entire sample.
The majority belonged to 20-40 yrs. of age comprising 58°Jo of the entire sample. The reason for this was that older subjects have had some ocular pathology in the past, men having cataract or glaucoma and hence could not be included in the series.
The range of normal intra-ocular pressure in the entire sample was from 9-21 mm. Hg. There were only two eyes having an intra-ocular pressure below 10 mm. Hg. i.e. only 0.330 of the entire sample. 26 eyes had an intraocular pressure of 20 mm. Hg. or more i.e. only 4.3% of the total number of individuals. The maximum difference recorded between the intra-ocular pressure of the two eyes of an individual was 3 mm. Hg.
The mean value for the entire sample was calculated at 15.33 mm. Hg. with standard deviation of 1.57.
The following table [Table - 2] shows the mean Intra-ocular pressure in different age groups.
From this table it is observed that there is a gradual rise of mean intro-ocular pressure with age till 60-69 years of age-group after which it shows a slight fall but this was also above the mean value for the entire sample.
The frequency distribution of the entire sample (Graph I) did not follow the normal biological or "Gaussion Curve".
The possible variation may be due to the fact that we are not dealing with a homogenous population but with a pooling together of sub-populations of different age groups and sex.
In order to analyse this point further, frequency distribution in each group was plotted separately. Out of three, only the first two groups showed a symmetrical curve to a good extent but after the age of 40 years even this symmetry was lost. This may be due to the fact that the size of the sample was also getting reduced with older age-group.
To study the effect of the influence of sex on normal intraocular pressure each age-group was subdivided into separate groups of males and females. The mean intra-ocular pressure according to age-groups in males and females is shown in Graph II.
Observing this it is found that the mean value for each group corresponds to the mean value for the entire sample in that there was a gradual rise in the mean intra-ocular pressure till 69 years of age after which there was a slight fall but still above the mean value for the entire sample. The mean value for the total male subjects in the sample was calculated as 15.01 mm.Hg. with standard deviation of 1.34.
The frequency distribution of intra-ocular pressure in females according to various age groups is also shown in graphic representation in Graph II.
Observing this graph it was found that there was gradual increase in mean value of intra-ocular pressure even till the last age group and there was no fall after 69 years of age as was noticed in the entire sample as well as in males. But at the same time there were only 2 females in the last age-group and this is not significant statistically because of the small number. The mean value calculated for total females was 15.68 with standard deviation of 1.86.
It was also observed from this study that the refractive condition had no definite relation with intra-ocular pressure by applanation tonometer.
The Effect of Family History of Glaucoma
There were 10 subjects who had positive family history of glaucoma, their age range was from 31-50 yrs.
The intra-ocular pressure was well within the range of their group except one who was 35 years of age had an intra-ocular pressure of 21 mm. Hg. and was subjected to further tests for glaucoma but all the tests proved to be negative in this particular case.
There were 9 subjects who had a reading of 21 mm. Hg. or more. The tests for glaucoma were carried out upon all of them. Five of them did not show any abnormality while four of them were diagnosed to be cases of early glaucoma.
| Discussion|| |
It is difficult to arrive at a particular figure from analysis and adopt it as a standard for a clinical study, but at the same time one should like to have some figures for guidance. Many authors have calculated the mean value in the past. The following table shows the range of intraocular pressure with Goldmann's Applanation Tonometer as marked out by various authors:[Table - 3]
It can be seen from the table that the range is from 13.70-16.3 mm. Hg. This is in excellent agreement with the mean pressure of 15.35 mm. Hg. recorded in the present series.
Various authors have rightly stressed the importance of the upper limit while screening patients for glaucoma. In the present series 4 cases of early glaucoma were detected and the highest tension recorded was only 26 mm.Hg. So if the upper limit was kept a little higher, then these cases would have easily been missed.
Another feature observed in the present series was that the maximum difference in the intra-ocular pressure between the two eyes was 3 mm. Hg. This should be kept in mind for the diagnosis of glaucoma, as a greater difference should give rise to a suspicion of glaucoma and the patient should be subjected to further tests for glaucoma.
Of greater interest and significance is the fact that males and females behaved in an identical manner in the two age groups (20--29 yrs. and 30-39 yrs.). The time of onset of this difference is of an especial biological significance as it coincides with the onset of menopause and it is thought that this greater increase in females is due to hormonal changes.
| Summary|| |
Applanation tonometry in 3C0 normal Indian subjects was done with the object of establishing a normal figure in males and females of different age-groups.
The observations are commented upon.
[Figure - 1], [Figure - 2]
[Table - 1], [Table - 2], [Table - 3]