Postoperative beta radiation treatment of pterygium

Abstract

A retrospective analysis of 69 patients with diagnosis of pterygium who underwent surgical removal of the pterygium and postoperative beta radiation from a Strontium-90 (Sr-90) applicator from January, 1973, to December, 1977, is presented. The radiation treatment was delivered 2–48 hrs postoperatively after surgical removal of the pterygium. Those few patients who received beta radiation after more than 56 hours postoperatively were not included in the analysis because of the small number of patients in this group. Thirty-two patients had bilateral pterygium; 18 patients from this group received radiation treatment to one eye only. A total of 83 eyes have been irradiated in the whole group. A total dose of 1800–2200 rad equivalent of beta radiation was delivered to the edge of the cornea and surgical bed of the pterygium in the conjunctiva. Measurement by phantom showed that the dose to the anterior surface of the lens will be approximately 70–90 rad, and the dose to the retina will be 4–8 rad during a single dose of 1800–2200 rad equivalent of beta radiation to the conjunctiva and pterygium bed. Thirty-nine percent of the nonirradiated eyes after removal of the pterygium developed recurrence, whereas only 5% of the irradiated eyes developed recurrence. Nineteen percent of the irradiated eyes developed cataract as well as 10% of the nonirradiated eyes. These include all detectable cataracts, some of which did not require lens removal. Local cortisone therapy reduced the progression of the recurrent disease for a few months and partial regression was seen in four eyes, but there was no complete regression of any recurrent pterygium with topical cortisone therapy. This retrospective study showed that postoperative 1800–2200 rad beta radiation from a Strontium-90 applicator, if delivered 2–48 hours postoperatively, is effective in reducing the recurrence rate. It has acceptable range of complication if it is administered by an experienced radiation therapist and calculation and calibration are done precisely. The immediate and late side effects and complications of beta radiation from a Strontium applicator are discussed, and the dose delivered to the cornea, sclera, lens, and retina with this radiation treatment are shown.