|Year : 1953 | Volume
| Issue : 2 | Page : 41-44
Experiences with beta radiation in ophthalmology
William John Holmes
|Date of Web Publication||15-May-2008|
William John Holmes
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Holmes WJ. Experiences with beta radiation in ophthalmology. Indian J Ophthalmol 1953;1:41-4
Beta radiation is a valuable therapeutic adjunct in the management of lesions of the anterior segment of the eye which heretofore resisted various forms of treatment. The following list of diseases have been reported to have responded to treatment with beta radiation with yawing degrees of success.
Superficial tumours that cannot be excised, especially papillomas of the lids and conjunctiva
Bowen's disease - intra-epithelial epithelioma
Angiomas of the lids
Pterygia - true, pseudo and recurrent and enlarged pinguecula
Vernal conjunctivitis and trachoma particularly trachomatous pannus
Vascularization of cornea (both to prevent and to obliterate corneal vascularization)
Prevention of revascularization of corneal stoma
Prior to told following transplantation
Interstitial keratitis due to syphilis and tuberculosis
Vascularized sclerosing keratitis
Traumatic keratitis -with scaring and vascularization
Post-herpetic disciform keratitis
Nummular keratitis with corneal infiltration and vascularization
Acne rosacea keratitis and Eczematoid kerato-conjunctivitis Corneal leukoma and deep Vascularization
No definite standards have been established regarding the exact amount of radiation for Various eye diseases. Likewise the total number of treatments, the intervals between treatments and the total amount of radiation for a given case often differ with each surgeon. In general, superficial lesions require less radiation and deeply seated lesions more radiation.
| Measuring Beta Irradiation|| |
Before considering the dosage for different conditions, a word may be said about the standard of dosage for calibrating the applicators.
For X-Ray therapy a dosage measurement which is dependent upon ionization in air has been established. This unit of measurement, the roentgen, is concerned with the ionization produced in a fixed mass of air as a result of incident N-rays or gamma rays.
This type of unit in addition, fits in well with the generally held belief that the biologic effects of radiation are due to ionization which is produced in tissue and the subsequent chemical effects resulting front such ionization.
Since a great deal of the biologic data concerned with the use of X-rays is in terms of roentgens, attempts have been made to utilize this unit, for the measurement of radiation dosage for all types of radiation and ionizing particles.
This has resulted more and more in the conception of an equivalent roentgen, which is a unit measure of ionization in tissue, or more directly, of energy absorbed in tissue from the incident radiation. This unit is called vaiously, the gram roentgen, roentgen equivalent physical (REP), or tissue roentgen. All these have the same basic concept - that is energy absorbed in tissue.
Friedell, Thomas and Krohmer (1950) in their original article recommended 300 REP'S weekly for four weeks until a total of 1200 REP's were .given. It soon became apparent that this amount of radiation was not sufficient to obliterate the blood vessels in a moderately vascularized recurrent pterygium.
Thomas later recommended 1000 REP's per week for three weeks or a total dose of 3000 REP's for conditions in which he had previously used 1200 REP'S. Friedell at this 'time was also using - higher dosages amounting to 1200 REP's pet, treatment five to, six tunes at weekly intervals for a total dosage of 3000 to 5000 REP's. Wilson and his co-workers (1952) found that the elimination of superficial vascularization might require as much as 12600 to 14000 REP'S. They have administered this in a single contact dose. With good ocular fixation and steady application, they felt that they obtained a safe and satisfactory clinical response its all areas except those where the vascularization was very deep. They believed that double this dose was definitely dangerous and might result in corneal ulceration and - even perforation of the globe.
Hughes (1946) felt that 20,600 REP's total dose applied anywhere on the globe was probably safe. He stated that even a total of 30,000 might be given in divided doses over several months time in cases where the clinical condition was of sufficient severity to warrant a slight, but nevertheless possible risk of producing a cataract.
Hughes recommended that each instrument be individually standardized on a few rabbit corneas to predict what to expect in clinical cases. He warned that in general the rabbit cornea was approximately three times more resistant to beta radiation than the human cornea. Thus a treatment which produced a barely perceptible nebular haze of the rabbit cornea might be Strong enough to eliminate corneal vascularization in men.
In experiments on rabbits Wilson and his co-workers (1950) found that when corneal ulceration occurred it developed as late as from the 94th to the 178th day after exposure. With radiation amounting to 80,000 REP's, they first noted corneal ulcers on the 28th day. Half this dosage, or 40,000 REP's, was responsible for corneal ulceration as late as the 181st clay. Perforation occurred from exposures of 35,000 to 80,000 REP's from the 52nd day (earliest) to the 244th day (latest). None of the rabbits in this series developed changes in their crystalline lens.
Hughes, in a forthcoming article, reports on two patients who developed ,cataracts approximately three years after beta radiation. His dosages were very high and would correspond to twelve exposures of 16.000 each, or a total of 192.000 REP's.
Friedell advised that the best method of calibrating the ideal dosage of an individual applicator is by the production of its skin erythema. According to his studies 500 REP's in 20 to 36 clays will produce a faint erythema; 1000 REP's will produce a well defined er1.thenta and 1500 will produce a sharp clearly defined unequivocal erythema with sonic scaling. These closes according to Friedell compare favourably with 500, 600 and 1500 Roentgens given by the 44KV Phillips contact machine.
My own practice, for the prevention and treatment of recurrent pterygia and obliteration of superficial corneal vascularization, has been to give 600 REP's every other day for five exposures, or a total of 3000 REP's. In a few instances where the vascularization was deep, as much as 6000 REP's were administered within ten days. If after six mouths, the clinical response was not satisfactory the first course, a total of 3600 REP's given in five closes, was repeated. If in twelve months time the disease still has not responded, the previous course of 3000 REP's was again repeated.
My usual dosage seldom exceeds 6000 REP's. The maximum dosage I have ever used was 12600 REP's. This was given for a pterygium which continued to recur after five operations.
Beta radiation alone in the treatment of recurrent pterygia was never sufficient in my hands. It always had to be combined with surgery. Beta radiation was applied to the denuded operative field immediately upon completion of the operation and on alternate days until the total dosage was given. The essential difference between my technique and that of most other surgeons is that I use radiation every other day while the majority use it at weekly intevals.
Each applicator is calibrated to possess a surface dosage of a given number of Roentgen equivalents per second, REP's.* The surface dosage of my own applicator corresponds to 30 REP's. If a total of 3000 REP's are desired for treatment of recurrent pterygium, this can be accomplished by giving five treatments, each treatment lasting twenty seconds (20 sec. x 36 REP's = 600 REP's; 600 REP 's x 5 treatments = 3000 REP's).
Technique ' The patient should be lying on his back in the prone position. The surgeon sits or stands at the head of the table. A few drops of ˝ % pontocain or any other desired topical anaesthetic is instilled into the eye. The lids are kept open with a speculum or with lid retractors. If lid retractors are used, they should be held at their distal ends, as far away from the operators fingers as possible. This is done to avoid the cumulative effects of scatter from beta radiation which may, over a long period of time, be injurious to the operator. In instances where the palpebral fissures arc narrow, there may not be enough room in the conjunctival cul de sac for insertion of both the speculum and the beta ray applicator. In these cases the applicator is applied to the desired portion of the globe and the lid margin is pushed away with the applicator simultaneously.
The patient is instructed to fix his gaze in the desired direction: temporalward if the nasal portion of the bulb is to be treated, nasalward if the temporal portion of the bulb is to be treated, etc. The applicator should rest on that portion of the globe which is to be treated. During the treatment if the patient moves his eyes out of contact with the applicator, the latter should be re-applied to its original position on the eyeball. The applicator is held gently without undue pressure on the eye. An assistant keeps time with an accurate secondhand watch.
Precise records are kept regarding the dates and the total number of REP's administered at each visit:
If several patients are to he treated, the unit is placed in the auxiliary shield. This should be filled with 1 : 3000 Zephiran or 1 : 5000 oxycyanide of mercury or any other desired antiseptic. Prior to treatment the tip of the applicator is wiped free of the antiseptic solution by diving it on a piece of gauze placed inside a small medicine glass. This method will further protect the operators hands from unnecessary exposure to beta radiation, and it will serve as a rapid means of getting rid of the moisture.
After the last treatment is finished, the applicator is dipped once snore in antiseptic solution, it is dried and stored in the original box. If desired, the entire box may be placed in still another box lined with lead.
During the past four years in over 200 patients I have not observed any temporary or permanent harmful side effects following beta radiation. Only a few patients have complained of smarting and burning sensations in their eves, which, however, subsided within a few hours.
| Summary|| |
An experience with a Beta Ray applicator utilizing SR" over a period of - four years on 200 patients is generalised with particular reference to pterygia. The limits of safe dosages for the eye are discussed.
| References|| |
Friedell, H. L., Thomas, C. I., and Krohmar, J.S. (1950) Am. J. Ophth. 33, 525-533.
Hughes, W. F., jr., and lliff, C.E. (1946) Am. J. Roentgen. 56, 502-517.
Lenz, M. (1950) Am. J. Ophth. 33, 46-51.
Okrainetz, C. L. (1950) Am. J. Ophth. 33, 52-62.
Petrohelos, M. A. (1952) Am. J. Ophth. 35, 637-645.
Ruedenran, A. 1). (1947 ) Arch. of Oplith. 38, 556-562.
Ruedenian, A. D. (1949 ) Arch. of Ophth. 41, 1-4.
Wilson, F. M. (1950) Am. J. Oplith. 33, 539-548.
Wilson, F. M. and Wilson, J. W. (1952) Arch. of Ophth. 48, 686-695.