|Year : 1970 | Volume
| Issue : 3 | Page : 118-124
Effect of oral glycerol on aqueous flow with perilimbal suction cup
P Awasthi, Gulshan Roy, SK Goel, RPS Bhatia
Department of Ophthalmology, Sarojini Naidu Medical College, Agra, India
Department of Ophthalmology, Sarojini Naidu Medical College, Agra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Awasthi P, Roy G, Goel S K, Bhatia R. Effect of oral glycerol on aqueous flow with perilimbal suction cup. Indian J Ophthalmol 1970;18:118-24
|How to cite this URL:|
Awasthi P, Roy G, Goel S K, Bhatia R. Effect of oral glycerol on aqueous flow with perilimbal suction cup. Indian J Ophthalmol [serial online] 1970 [cited 2021 May 6];18:118-24. Available from: https://www.ijo.in/text.asp?1970/18/3/118/35075
Rosengren described a suction cup which he placed on the limbal area and maintained a negative pressure of 100 mm Hg. for 15 minutes resulting in rise of intraocular pressure, but the mechanism was not known. Ascher  and Huggert  reported disturbances in the circulation of aqueous veins and increased intraocular pressure in both normal and glaucomatous eyes by the use of contact lenses with heptic fitting. These observations stimulated Rosengren to repeat his experiments after a lapse of 22 years. This time the intention was to obstruct the outflow channels.
Occlusion of outflow channels by suction cup leads to an obvious rise in intraocular tension. From this observation, various workers (Ericson  , Linner  , Weekers, Crijot, Zeron and Varrier  , Langham  and Chandler  have estimated the rate of aqueous formation with the help of Friedenwald's table. The present study was undertaken to find out the rate of aqueous flow in normal eyes and in chronic simple glaucoma cases, before and after glycerol therapy.
| Method and Materials|| |
Control observations were derived from 20 normal subjects who attended the ophthalmic out patients department, S. N. Hospital, Agra with refractive errors. These patients had no family history of glaucoma, with normal fields, fundus, tension and angle of filtration and had no systemic disorder like diabetes, hypertension etc.
20 glaucomatous patients were: picked up from the Ophthalmic out patient department and the Glaucoma Clinic of the Department. They were established cases of chronic simple glaucoma with raised intraocular pressure, field changes and fundus findings varying from nasal shifting to marked glaucomatous cupping.
Throughout this study, a standard suction cup was used. Its inner diameter was 13.5 mm, outer 19.5 mm, contact surface 3 mm, and the radius of curvature 12.32 mm. The weight of the cup was 1.8 gm. The suction cup was connected to a suction apparatus with interposition of a mercury manometer.
All the estimations were: carried out at the same time of the day usually between 4 P.M. and 8 P.M. The patient was required to lie recumbent facing the ceiling. The eye was anaesthetised with Anaethaine 1 % drops. The tension was taken with certified standard Schiotz tonometer (initial tonometer reading). The suction cup was applied and a negative pressure of 50 mm Hg. was maintained for 15 minutes. The cup was taken off and tonometry was done again (2nd tonometer reading). There after tonometery was repeated every 5 minutes until the initial tonometeric reading was reached. The time of regression was noted.
In chronic simple glaucoma cases all the and-glaucoma drugs were stopped, 72 hours before the administration of glycerol. Aqueous flow measurement was done before glycerol therapy and was repeated 1 hours after the administration of glycerol. Glycerol was given orally in the dosage of 1.5 gm/kg. of the body weight as 50% solution in normal saline, flavoured with orange juice and cooled in a refrigerator.
The volumes corresponding to the initial and 2nd tonometer reading were obtained from the Friedenwald's table. The difference in volumes gives the amount of aqueous formed in cubic/ml. in 15 minutes from which the rate of aqueous formation per minute was calculated.
The volume of aqueous formed in 15 minutes was divided by the regression time to get the rate of aqueous drainage per minute.
| Observations|| |
Aqueous flow measurements in normal eyes
The rate of aqueous formation was found to vary from 0.0693 to 1.006 cml/mt with an average of 0.776 cml/mt. The rate of aqueous drainage ranged between 0.401 cml/mt and 0.665 cml/mt the average being 0.516 cml/mt. Time required to reach the initial tension varied from 15 to 25 minutes with an average of 21.75 minutes [Table - 1].
Aqueous flow measurements in chronic simple glaucoma eyes before and after glycerol therapy
A. Before glycerol therapy:- The rate of aqueous formation ranged between 0.321 cml/mt and 0.660 cml/ mt, the average being 0.472 cml/mt. The rate of aqueous outflow varied from 0.120 cml/mt to 0.330 cml/ mt and averaged 0.217 cml/mt. Time needed to reach the initial level of tension varied from 25 to 40 minutes the average being 34.5 minutes [Table - 2].
B. After glycerol therapy:- The rate of formation ranged between 0.232 cml/mt and 0.532 cml/mt. with an average of 0.358 cml/mt. So the average reduction in the rate of inflow was 0.114 cml/mt. The rate of drainage varied from 0.149 cml/mt to 0.390 cml/mt, the average being 0.220 cml/mt. So the average increase in the rate of drainage was 0.003 cml/mt i.e. it was negligible. Time required to reach the initial level of intraocular pressure was found to vary from 20 to 30 minutes with an average of 24.25 minutes [Table - 3].
| Discussion|| |
In this study 20 normal eyes were studied as control and 20 established cases of chronic simple glaucoma were subjected to suction cup technique before and after glycerol therapy.
The age of the normal subjects varied from 41 to 59 years, the average being 50.75. The patients of this age range were selected because glaucoma patients belonged to this age group. The tension in these eyes ranged between 15 mm and 22 mm Hg with an average of 18.65 mm. Hg.
The average rate of aqueous formation was found to be 0.776 cml/ mt. Linner and Ericson also obtained a similar value by the same technique.
This value is in sharp contrast with the values obtained by Goldmann  and Grant  . Goldmann  found 1.9 cml/mt using the fluorescein technique and Grant  measured 1.3 cml/mt. employing tonography. This low estimation would be due to the fact that the pressure of the cup itself causes a rise of 4 mm Hg. in the intraocular tension and the continuous rise of ocular tension during cup application tends to slow down aqueous formation.
The average rate of aqueous drainage was 0.516 cml/mt.
The age of the glaucomatous patients varied from 37 to 60 years the average being 50.4. The tension ranged from 28 mm Hg. to 50 mm Hg. with an average of 37.85 mm Hg.
The average rate of aqueous inflow was 0.472 cml/mt. The figure is lower than the figure in normal eyes (0.776 cml/mt). This can be explained on the basis of the view held by Lytton  that the production of aqueous is automatically regulated depending on raising or lowering of intraocular pressure.
The average rate of aqueous outflow was found to be 0.217 cml/mt. This value is much lower than the value obtained in normal eyes (0.516 cml/mt). This can be attributed to the resistance to the aqueous outflow at the angle of filtration. In chronic simple glaucoma decreased production of aqueous compensates to an extent for the increased resistance to the aqueous outflow and new equilibrium at a raised tension level is established.
The time required to reach the initial tension was 34.6 minutes which is higher than in normal eyes (21.75 mts). This is because of the greater resistance at the outflow channels.
In chronic simple glaucoma after glycerol therapy, the average rate of aqueous inflow was 0.358 cml/mt. outflow was 0.222 cml/mt.
So in the present study it has been observed, that the average reduction in the rate of aqueous formation was 0.114 cml/mt varying from a maximum reduction of 0.314 cml/mt to a minimum of 0.013 cml/mt The increase in the rate of aqueous drainage was on an average of 0.003 cml/mt. with a maximum of 0.143 cml/mt. and a minimum of 0.012 cml/mt. The average drop in the tension was 14.8 mm Hg. with a maximum of 20 mm Hg. and minimum of 12 mm. Hg.
Besides these observations, a few facts were revealed in connection with the use of glycerol. Glycerol is found to be very effective ocular hypotensive drug with milder side-effects (nausea in few cases, mild headache in four patients and diarrhoea in one patient). As given by oral route it avoids the danger of I/V transfusion as are associated with drugs like urea and mannitol. The maximum effect of glycerol occurred in 90 minutes with the dosage of 1.5 gm per kg of the body weight.
| Summary and Conclusions|| |
20 normal and 20 chronic simple glaucoma patients were subjected to suction cup technique to find out aqueous flow measurements. In chronic simple glaucoma eyes the rate of aqueous inflow and outflow was determined before and after the administration of glycerol.
On critical evaluation of the observations the following conclusions were derived
1. Glycerol acts by reducing the rate of aqueous formation.
2. Glycerol does not show any noticeable effect on the rate of aqueous drainage.
3. The reduction in the rate of aqueous formation was proportional to the range of tension, irrespective of the disease process. Other significant observations were:
(a) In chronic simple glaucoma eyes, the average rate of aqueous inflow and outflow was lower than in normal eyes.
(b) Glycerol is a very potent hypotensive drug with few mild side effects.
(c) The maximum effect of glycerol occurs 12 hour after the administration of the drug with the dosage of 1.5 gm/kg. of body weight.
(d) The suction cup technique proves that there is a reflex inhibition of aqueous formation in advanced cases of chronic simple glaucoma patients.
| References|| |
Aschar, K. W. (1951) : Arch Ophth. 44, 365 (1951).
Chandler, M. R. (1964) : Brit. J. Ophth. 48, 423.
Eriscon, L. A. (1958) : Acta Ophth. (Kbn) Suppl. 50 (quoted by 12).
Goldmann, H. (1950) : Ophthalmologica (Basal) 119, 65. Cited by Duke Elder.
Grant, W. M. (1950) : Arch Ophthal. (Chicago) 44, 65.
Huggert (1953): Acta Ophthal. 31, 141.
Langharn, M. E. (1962) : Invest. Ophthal. 1, 484.
Linner, E. (1959) : A. M. A. Arch Ophthal. 51, 520.
Lytton (1956) : Brit. J. Ophthal. 40, 104.
Prijot, E. (1958) : Docurn Ophthal, 13, 193.
Rosengren, B. (1956) : Trans Ophthal. Soc. U. K. 76, 65.
Weekers, R., Prijot. E., Feron, A. and Varrier (1960) : Acta Ophthal. (Kbh) 38, 129.
[Table - 1], [Table - 2], [Table - 3]