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To the Editor:
—My attention has been directed to an article by Dr. J. W. Bettman, in A. M. A. Archives of Ophthalmology (59:821 [June] 1958), entitled Radioactive Isotopes.I quote from page 825 paragraph 15: "The therapy of intraocular tumors, usually retinoblastomas, by suturing radioisotopes to the sclera,29,31,34... is not new.... They depend upon β-emissions for their therapeutic effect, the α-emissions not penetrating the eye and the γ-emissions being very weak." The three references given here include one to an article by Dr. Arthur Joyce and myself entitled Treatment of Intraocular Tumors with Radon.This statement concerning radon seeds which we use is not correct.The radon seeds are prepared by the Commonwealth X-ray and Radium Laboratory and have wall thicknesses of gold equivalent to platinum filtration of either 0.3 or 0.5 mm.No α-rays are emitted, the β-rays contributions through the above filtrations are approximately 10% and