THE EFFECT OF EXTERNAL EYE IRRADIATION ON CHOROIDAL CIRCULATION

Background: The effect of external beam radiation therapy (teletherapy ) on the choroidal circulation is poorly known. Eyes irradiated with t eletherapy represent a good model to study, without confounding factor s, the pathophysiologic and clinical aspects of radiation-induced chor ioretinal damage. This study used fluorescein and indocyanine green ch oroidal angiography to investigate the late effects of external eye ir radiation on the choroidal circulation, Methods: Fluorescein angiograp hy and indocyanine green choroidal videoangiography were performed on patients with radiation retinopathy because of external eye irradiatio n for orbital and paranasal sinus malignancies, Patients were divided into two groups according to the treatment field (anterior unilateral or bilateral). Results: Indocyanine green angiograms showed areas of c horiocapillaris hypoperfusion in all eyes - unilateral or bilateral ir radiation - affected by radiation retinopathy. Late indocyanine green choroidal staining was found in five eyes (28%) of the patients who re ceived unilateral anterior irradiation. In the same group, nine eyes ( 52%) had signs of choroidal precapillary occlusion and four eyes (23%) had rubeosis iridis without retinal neovascularization. One case of s ubfoveal choroidal neovascularization was documented in the bilateral irradiation group. Conclusions: Radiation side effects are not limited to the retinal vessels but also involve choroidal circulation. The da mage to the choroid is primarily vascular, and its clinical aspects de pend on the treatment fields. Anterior irradiation may be a critical f actor for the appearance of unusual rubeosis iridis and neovascular gl aucoma.