|Year : 1992 | Volume
| Issue : 1 | Page : 27-28
Use of beta radiation to control I.O.P.
Shabbir Saifuddin Adenwala, L Otto Erich
Augenlinik Der University Munchen, Mathilden Str. 8, Munchen 2, Federal Republic Of Germany
Shabbir Saifuddin Adenwala
PO. Box 2896. Dubai, UAE
Source of Support: None, Conflict of Interest: None
The use of ophthalmic applicator containing Strontium-90 beta ray was used to bring about a change in I.O.P by its effect on the ciliary body. The change in 1.0.11 depends on the degree of damage done to the ciliary body. The study showed that the change in 1.0.11 was directly proportional to the intensity of beta rays application - higher the dose of beta radiation more was the damage and more the reduction in 1.0.P.
|How to cite this article:|
Adenwala SS, Erich L O. Use of beta radiation to control I.O.P. Indian J Ophthalmol 1992;40:27-8
| Introduction|| |
The method of freezing or heating the ciliary body destroys it or cuts the blood supply thereby decreasing the production of aqueous humour. The same principle applies to the use of beta radiation as a therapeutic measure to control I.O.P. This new method, accidentally found after the use of beta radiation for post-operative pterygiurn, is among the numerous surgical procedures commonly employed to control I.O.P. by diminishing the formation of aqueous humour.
| Material and methods|| |
Nine cases of bilateral primary open angle glaucoma were used in this study ( 6 females and 3 males of age group 52-65 years). An ophthalmic Strontium-90 beta ray applicator, type SIA-20 (Amersham production) was used as the source of beta radiation. It had an average surface dose rate of 50 rads/second at the time of study. The active dose is mounted on a handle which allows rotation through 180 degrees. It has a kidney shaped aperture which helps to limit the size of the irradiated area. Aperture is of 2 mm breadth and 8 mm length. I.O.R was measured using an applanation tonometer.
I.O.P was first measured and then the upper third of the circumference of the ciliary body was exposed to irradiation. Three adjacent trans-conjunctival beta ray applications adjacent to each other at the limbus for 3 minutes each to give a total exposure time of 9 minutes and 270 Gy closer were employed. Two patients with higher I.O.P were given a higher dose for a total time of 12 minutes and 630 Gy dose.
Post irradiation I.O.R was measured for the treated eyes which was performed on the same day ( 2 hours and 6 hours after the irradiation), 2nd day, 7th day, 14th day, 21st day and 45th day.
| Results|| |
There was significant decrease in I.O.R on the second day post-irradiational and further decrease subsequently to attain the maximal effect after 3 weeks [Table - 1]. No complications were seen except in two cases where there was conjunctiva congestion and oedema and in another where there was some ciliary congestion.
| Discussion|| |
Though the recently accepted definition of normal I.O.P is that which does not cause any pathological damage to the ocular tissues but numerically anything greater than 22 mm Hg is considered suspicious if not completely abnormal . Other than for angle closure glaucoma, various methods are used in the management of different types of glaucoma, the methods depend on two factors. The first is to improve the outflow of aqueous for which infinite number of techniques are used. The other method is to decrease the production of aqueous which is produced by the ciliary body. It is an established fact that moderate irradiation to any secretory cells in the body may lead to diminution of secretion.
The use of Strontium-90 beta ray applicator was to destroy the ciliary body incompletely thereby decreasing the production of aqueous humor.
Strontium-90 beta applicator has a nominal activity of 55 millicurie and about surface dose rate of 50 rads/second, the maximal beta energy is 2.27 Mev. (million electron volt) the active surface is plane, an advantage over the spherical surface in which the chances of getting cataract are higher . The use of the mentioned type of applicator is much safer than any other type.
The results showed there was definite decrease in I.O.P with the use of beta radiation and this was probably due to the effect of radiation on the secretory cells of the ciliary body and their blood supply, thereby decreasing the aqueous formation. Also there is hydropic degeneration in the ciliary epithelium and obliteration of blood vessels of the ciliary body as a result of endarteritis obliterans .
Clinical follow up for cataractous changes was not possible because it may occur after a very long latent period of 2-15 years after the irradiation but the radiational cataract after beta radiation remains peripheral and stationary and thus does not affect the vision .
The probability of cataract formation as mentioned in the literature can well be avoided by the use of a kidney shaped aperture with its inner edge parallel to the limbus which restricts exposure to the ciliary body only without any exposure to the lens.
This new non-invasive technique can be tried to reduce I.O.P before any surgical methods are employed.
| References|| |
Deborah. PL. : Manual of ocular diagnosis and therapy. A Little. Brown Co . 2nd edition. 1987. 203.
Supe, S.J. : Malikajuna, S. and Swant. S.G. : Dosimetry of spherical Sr. 90-y90 B-ray eye applicators. Am. J. Roentgenol Radium their Nucl. Med., 123 (1): 36-41, 1975.
Dobrovolskaia-Zavadskaia, N.A. : Action des Foyers radioactive. Sue Les vaiseaus sanguins. An,. J. Ophthalmology. 33-36. 1950
Lommatzch, P : Correns. H J. and Neumeister, K. Radiogenic application of B-radiation. 14th Annual Meeting of European Society of Radiation Biology held in Julich. W. Germany, 113, 1978.
[Table - 1]