|Year : 1974 | Volume
| Issue : 1 | Page : 15-20
Intraocular pressure dynamics in different refractive errors
IS Jain, J Chaudhry
Department of Ophthalmology, Postgraduate Institute of Medical Education & Research, Chandigarh, India
I S Jain
Department of Ophthalmology, Postgraduate Institute of Medical Education & Research, Chandigarh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Jain I S, Chaudhry J. Intraocular pressure dynamics in different refractive errors. Indian J Ophthalmol 1974;22:15-20
|How to cite this URL:|
Jain I S, Chaudhry J. Intraocular pressure dynamics in different refractive errors. Indian J Ophthalmol [serial online] 1974 [cited 2020 Jun 1];22:15-20. Available from: http://www.ijo.in/text.asp?1974/22/1/15/31386
In past glaucoma in myopic eye was missed until it had reached an advanced stage. Several reasons had contributed to this, e g. low scleral rigidity and difficulty in the interpretation of changes associated with glaucoma.
With the development of the technique of tonography, the problem of diagnosing glaucoma entered a new field. Bock and Stepnaik  established the diagnosis of glaucoma in myopic eyes with the help of tonography. Palazi  found that in highly myopic eyes, the coefficient of facility of outflow was consistently lower than that in emmetropic eyes, but was not pathological.
It becomes important to know, whether this altered aqueous dynamics is in myopic eyes only, or any relationship exists between aqueous dynamics and various refractive states.
There have been isolated reports about various aspects of aqueous dynamics in eyes with different refractive errors. Jain and Singh  studied the aspect of tension by Schiotz method and Muto Koki et a1  found out the coefficient of outflow in eyes with different refractive errors. Distribution of applanation tension in eyes with different refractive errors have also been studied by various workers ,, ..
The present study was undertaken to know all the aspects of aqueous dynamics in different refractive errors comprehensively.
| Material and Methods|| |
Two hundred eyes of 100 healthy subjects were selected [Table - 1]. Such subjects had no ocular pathology except for refractive error.
The following five groups were made:
(A) High myopia group: Myopia more than -6.00 D.
(B) Moderate myopia group: Error varying from -0.25 D to-6.00 D.
(C) Emmetropia group : Error within the range of±0.25 D.
(D) Moderate hypermetropia group : Error ranging from-0.25 to -4.00 D.
(E) High hypermetropia group : Error more than-L4.00 D.
Each case was processed as under
(i) Refraction was done under cycloplegia with Homatropine 1% drops.
(ii) Intraocular pressure was recorded by Schiotz tonometer using plunger weight of 5.5 gms. and by Goldmann applanation tonometer.
(iii) Tonography was performed with V. Mueller electronic tonography apparatus.
(iv) 'c' value was calculated by Becker's weight table and Friedenwald's nomogram (1955).
| Observations|| |
It was observed that average intraocular pressure by applanation method in each refractive error group was higher than by Schiotz method. In high myopia group average intraocular pressure by Schiotz and applanation method was higher than average intraocular pressure in moderate myopia group. It was 17.76±1.72 mm Hg by applanation and 15.62-1--2.47 min Hg by Schiotz in the high myopes, whereas in moderate myopes it was 16.19±2.08 mm Hg by applanation and 15.00±2.42 mm Hg by Schiotz. The difference of tension by Schiotz and applanation method was statistically highly significant in high myopia (P<0.01) and statistically significant in moderate myopia (P<0.05) [Table - 3]. In emmetropia group, average applanation intraocular pressure was 15.68±2.00 mm Hg and 14.92 + 2.71 mm Hg by Schiotz. Intraocular pressure by both methods (applanation and Schiotz) in high hypermetropia was higher than in moderate hypermetropia group [Table - 2].
Average intraocular pressure by applanation and Schiotz method in high hypermetropia group was 14.22±1.89 mm Hg and 14.19 + 2.55 mm Hg respectively and in moderate hypermetropia group these figures were 13.31 + 2.29 mm Hg and 12.96 + 2.89 mm Hg respectively.
The distribution of the `C' value in different refractive errors is shown in [Table - 4].
| Discussion|| |
The observations are discussed under the following subheadings : Schiotz tension, applanation tension and 'C' value.
In our series, mean intraocular pressure in emmetropic eyes was higher than that reported by Kruse  and Saeteren  , but lower than those reported by Becker  , Graham and Hollows  and Badlani and Telang  .
Average intraocular pressure readings in hypermetropic eyes were higher and in myopic eyes were lower than those reported by Jain and Singh  . However, we agree with the report of authors that intraocular pressure by Schiotz method in hypermetropic eyes is lower and in myopic eyes is higher than in emmetropic eyes, but differ from them in that average intraocular pressure in high myopia group is lower than that in moderate myopia.
Average applanation tension in emmetropic subjects was 15.68_!-2.00 mm Hg. These figures are obviously higher than those reported by other workers ,,, but these values are in complete agreement with the readings of Goldmann et a1 and Chopra et al. As compared to Graham and Hollows  and Weeker et al, they are on the lower side.
Average intraocular pressure in moderate myopia and high myopia group was 16.19 + 2.08 and 17.76± 1.72 mm Hg respectively.
Our findings are higher than those reported by other workers ,, .
We are in complete agreement with Koki Muto et a1; Abdalla and Hamdi  and Tonlinson and Phillips  that average applanation tension in myopes is higher than in emmetropes. However, we do not agree with Caso  , Kraupa  and Pooo  who reported low intraocular pressure in myopic eyes. Higher incidence of chronic simple glaucoma in myopia was not substantiated by our study as reported by Riaz  and Podos et al.
Our findings for both moderate and high hypermetropes are higher than those reported by Koki Muto et a1 and Tonlinson and Phillips  , but our average applanation tension value for moderate hypermetropia is a little lower than that found by Tonlinson and Phillips  .
We agree with Tonlinson and Phillips  that intraocular pressure in hypennetropes was lower than in emmetropes. We do not agree with Draeger  , Lavene  , and Chopra et al who found rise of intraocular pressure with age.
Co-efficient of Facility of Outflow
Our figures of average `C' value for normal (emmetropia) eyes were higher than those reported by Becker and Christensen, Leydhecker  , Prijot  and Koki Muto et al.
Our figures of average `C' value in myopic eyes were higher than those reported by Koki Muto et al. In our study, lower limit of `C' value in myopic eyes was 0.258+ 0.077 as against the figures (0.212±0.041) reported by the above authors. Our highest figures of 'C' value in myopic eyes were also higher (0.31+0.099) than those reported by some workers (0.270±0.093). Our observations are in agreement with the findings of Palazi and Koki Muto et al that although 'C' value was low in myopes in comparison with emmetropes but it was not below the accepted limit of normal (0.18).
| Conclusions|| |
Following conclusions have been drawn from this study
- Intraocular pressure by both Schiotz and applanation methods is higher in myopic eyes and lower in hypermetropic eyes than in emmetropic eyes.
- Intraocular pressure is higher in high myopes than in moderate myopes and lower in moderate hypermetropes.
- Intraocular pressure is higher by applanation method in 710 of eyes and by Schiotz method in 20.5% of eyes, while there is no difference of the tension by two methods in 8.5% of eyes.
- Difference of intraocular pressure by two methods is highly significant in high myopes as well as in moderate myopes, but the difference is not significant in emmetropic and hypermetropic eyes. This underlines the importance of recording of intraocular pressure by applanation method in myopes.
- 'C' value is lower in myopic and hypermetropic eyes as compared to emmetropic eyes. 'C' value, however, does not fall below the accepted lower limit of normal in myopic eyes (0.18).
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[Table - 1], [Table - 2], [Table - 3], [Table - 4]