[Dose distribution during irradiation of the retrobulbar space--results of measurements on a phantom].

The transverse dose distribution in case of X-ray and cobalt irradiation of the retrobulbar space was measured in a water phantom. As expected, the crystalline lens receives a smaller dose by cobalt irradiation with lead shielding in front of the eye than by X-irradiation. In case of cobalt irradiation, the dorsal portions lying within the hypophyseal region can only be sufficiently protected by a special block cast by us in a divergent form and surrounding the irradiation field. If X-ray irradiation is performed with a field size of 2 X 4 cm2, the 50% isodose encloses just the complete retrobulbar space. Taking into consideration a second contralateral field, the crystalline lens is exposed to less than 10% of the maximum dose. Thus the doses applied usually in radiotherapy of endocrine ophthalmopathy, i.e. 15 to 20 Gy, lead to an unproblematic crystalline lens exposure of 150 to 200 rad.