|Year : 1975 | Volume
| Issue : 2 | Page : 1-6
Rate of aqueous formation during normal menstrual cycle
RL Vaid1, Hamida Buchh1, Lila Ahuja2, Vijay Wali1
1 Government Medical College, Srinagar, Kashmir, India
2 Institute of Ophthalmology, A.M.U Aligarh, India
R L Vaid
Department of Ophthalmology, Government Medical College, Srinagar, Kashmir
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Vaid R L, Buchh H, Ahuja L, Wali V. Rate of aqueous formation during normal menstrual cycle. Indian J Ophthalmol 1975;23:1-6
Salvati  as early as 1923, noted an increase in intraocular pressure during normal menstural cycle. Stray reports have been appearing stressing that a relationship does exist between various phases of menstrual cycle and. aqueous humour dyanamics. Shahan  reported a small but definite cyclic variation in the facility of outflow: which was also reported by other workers ,, . These reports in addition to that of Dalton  , Lagrenge  and Weinstein  stressing the time relationship of menstruation and symptoms of angle closure glaucoma, point to a definite relationship between these two; the basis of which is still not understood. Perkins  has pointed out that incidence of glaucoma although, lower in premenopausal females as to males in corresponding age group, tends to be equal in both in the post-menopausal period. Similar observation was made by Said-uz-Zafar and Vaid  about the facility of outflow which was higher in premenopausal females but was similar to that in males in the post-menopausal period, in the corresponding age groups.
This problem was found interesting enough to carry out a comprehensive study in the normal females, to establish the basis if possible, on which the hormonal variations, influence the aqueous humour dynamics. Intraocular pressure in normal persons is dependant mainly on facility of outflow, ocular rigidity and rate of aqueous formation. On study of these three aspects, it was found that despite of the significant changes in the facility of outflow  the intra-ocular pressure was not significantly affected. As the ocular rigidity also does not vary significantly  , only other factor which could have been responsible was the rate of aqueous formation. In this paper an effort has been made to assess the effect of variations in. the hormonal values normally occuring in the normal menstrual cycle, on the rate of aqueous formation vis-a-vis its relationship with facility of outflow.
| Material and method|| |
60 women included in this study, were selected from the patients attending the Gandhi Eye Hospital, for refractive problems. They were thoroughly examined to rule out the possibility of glaucoma and any other concurrent ocular disease. Complete gynaecological history was taken and the selected cases had normal and regular menstrual cycles. The cases with menstrual irregularities were not included in this study. The cases were divided in three sub-groups on basis of age as shown in [Table - 1].
Intraocular pressure of all the 120 eyes of 60 cases was recorded by applanation tonometer and tonography was performed using Schwarzer's self recording onographic equipment. Facility of outflow was calculated in each case using Friendwald's (1955) nomogram on the 1st, 7th, 14th, 21st and 25th day of the normal menstrual cycle and the rate of aqueous formation was calculated by using the following formula F=C (Po-Pev); where F is rate of aqueous formation in ul/mt., C is the facility of outflow in uI/mt/mm. Hg., Po is the original intraocular pressure recorded by applanation tonometer and Pev is the episcleral venous pressure. The episcleral venous pressure is reported to vary from 8 to 12 mm. Hg. ,,, but in our study, 10 mm. Hg was taken as the mean value for the purpose of calculations. The values thus obtained were analysed and the results are shown in [Table - 2] and [Figure - 2]. The values then obtained were compared with the C values already reported  in the [Table - 4], to assess if any correlation exists or not. In [Table - 3] the data obtained have been subjected to statistical analysis as to the significance of differences in the rate of aqueous formation.
| Results and Discussion|| |
There are various methods available to measure the rate of aqueous formation, but topography is the one which is the simplest and can be applied to human beings, the values thus obtained are in considerable agreement to the ones obtained by other methods  . The values for the aqueous humour formation were calculated on 1st, 7th, 14th, 21st and 25th day as these days are known to correspond with the known and well established, variations in oestrogen and progesterone levels during the normal menstrual cycle. [Figure - 1] is based on the well established values of oestrogen and progesterone during various phases of normal menstrual cycle and shows that oestrogen content has two clearly defined peaks and during the normal menstrual flow the oestrogen is at very low level rising to a peak two days prior to ovulation, followed by a steep fall. The second peak lower than the first occurs during the luteal phase, decreasing three to four days prior to the onset of menstrual flow. The progesterone on the other hand is present in very small quantities during the first half of the cycle followed by a rapid increase in second half after ovulation, reaching its minimum two to three days before the start of menstrual flow. The withdrawal of these hormones is followed by menstruation. So during the normal menstrual cycle, the values of the ovarian hormones vary during different stages and this variation when worked out in relationship to the days of menstrual cycle, shows that on the first day of menstrual cycle the progesterone is nearly absent while oestrogen has gradually started increasing in amount. On 7th day while progesterone is still nearly absent, the amount of oestrogen is nearing its peak value. Ovulation as a routine takes place from 12th to 16th day, so on average it is assumed to occur in 14th day, then two days before the ovulation, the oestrogen having reached its value decreases rapidly. On 14th day the oestrogen is present in small amounts while progesterone starts appearing i.e. both the ovarian hormones are in minimal quantities. On 21st day the progesterone is rapidly increasing alongwith the second oestrogen peak, which is smaller than the first. On 25th day both the ovarian hormones have dropped to minimal levels so that menstrual flow can take place in 2-3 days time.
So 1st, 7th, 14th, 21st and 25th days were chosen as these coincided with definite hormonal phases in menstrual cycle and on these days tonographic studies were made to know the values for the facility of outflow and the rate of aqueous formation. The results of the study of facility of outflow have already been published.
[Table - 2] shows that there is definite decrease in the rate of aqueous formation on 14th and 25th days as compared to 1st or 7th day and this decrease of the aqueous flow was uniformly present in the main group as well as in all the sub groups. On statistical analysis and on applying the significant test (T. test) this decrease was found to be significant. [Table - 4] and [Figure - 2] show the relationship of the inflow value with the outflow value and it is clear that both the values decrease on the 14th and 25th day i.e. the days on which the levels of oestrogen and progesterone are minimal and it is clear that outflow value decrease simultaneously with decrease in the inflow value, the cause appears to be a compensatory adjustment in the outflow value or there may be an ill understood mechanism, neural, humoral or otherwise which controls both the values, but at the moment compensatory adjustment appears to be the main factor, that is why that in spite of significant decrease in outflow value 25 intraocular pressure is not significantly altered as the decrease in outflow value is secondary to )r associated with decrease in inflow value.
What could be the probable cause and how does the variation in values influence the rate of aqueous formation ? The rate of aqueous formation and facility of outflow are known to decrease with the advance in age.  , According to Becker  it is not known whether these are independant or related to each other, he has reported that a decrease in rate of aqueous formation results in the decrease in the facility of outflow. His hypothesis that decrease in inflow may decrease the nutritional supply of trabecular mesh work and may result in permanent or temporary alteration in trabecular mesh work causing variation in outflow value. The rate of aqueous formation is known to vary as diurnal variation  and is inhibited by the intraocular surgery, especially cyclodialysis, cyclodiathermy, after cataract extraction  and a decrease has been reported after surgery on intraocular muscle. No convincing evidence of neurovascular control has been reported and studies have revealed that interruption of sympathetic nerve supply has no effect on it it, ,, . Hormonal control of aqueous formation has been reported, following adrenalectomy the fall in the inflow value occurs which has been attributed to derangement of Redox pumps  . On the other hand, the value is reported to increase on the local use of synthetic steroids. It has been suggested that the inhibition of aldosterone resulted in decrease in rate of aqueous formation  . It is clear from these observations that in addition to various factors the aqueous formation is also influenced by the hormones. In present study the rate of aqueous formation is clearly running parallel to the amount of oestrogen and progesterone and is seen to decrease when the hormones are present in minimzl amounts. Mode of action whether it is a biochemical one or neuro-vascular one is difficult to say. A diminution in ophthalmic arterial pressure has been reported under the influence of oestrogen  . On the other hand, the capillary permeability is reported to vary throughout the course of menstrual  cycle while on experimental studies in rabbits oestrogen in extremely high concentration has been reported to decrease the vascular permeability  . Whatsoever may be the mode of action, but it is clearly seen that the presence of oestrogen and progesterone increases the amount of aqueous formation (although within normal range) and a decrease in their levels causes a decrease, the change being statistically significant [Table - 3]. The decrease in aqueous formation results in reciprocal or concurrent significant decrease in the facility of outflow  , thus maintaining the intra-occual pressure within normal limits.
The reason and the basis for this alteration is not known and it is hoped that in near future this riddle could be solved.
| Summary|| |
Tonographic studies were made on 120 cases of 60 normal women with regular menstrual cycle on 1st, 7th, 14th, 21st and 25th day of the menstrual cycle.
The rate of aqueous formation was calculated on the basis of facility of outflow, which was obtained using Friedenwalds normogram. The results obtained were statistically analysed and showed a significant variation in the rate of aqueous formation which when correlated with the values of facility of outflow, explained the variation in later, as both run parallel to each other and appear to be influenced by hormonal variations.
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[Figure - 1], [Figure - 2]
[Table - 1], [Table - 2], [Table - 3], [Table - 4]