Late ophthalmological complications after total body irradiation in non-human primates

Abstract

Purpose : To investigate the long-term eff ects of total body irradiation (TBI) on the incidence and time course of ocular complications. Materials and methods : Rhesus monkeys treated with TBI photon doses up to 8.5Gy and proton doses up to 7.5Gy were studied at intervals up to 25 years post-irradiation. They were compared with control groups with a similar age distribution. Cataract formation and ocular fundus lesions were scored according to a standardized protocol. Fluorescein angiography and histopathology was performed in selected animals. Results : Cataract formation occurred after a latent period of 3-5 years. Significant cataract induction was observed for photondoses of 8 and 8.5Gy and beyond 20 years after proton irradiation. The severity of the lesions represents significant impairment of vision and would require cataract surgery if similar results occurred in human bone marrow transplant patients. Fluorescein angiography demonstrated a normal pattern of retinal vessels in 13 out of 14 animals (93%) from the irradiated group and in eight out of nine animals (89%) from the control group. No additional lesions apart from age-related degenerative changes could be demonstrated. Histological evaluation revealed no radiation-associated vasculopathy. Conclusions : Radiation alone for doses up to 8.5Gy of photons does not carry a potential risk for fundus pathology, whereas clinically important cataract induction should be anticipated within 5 years after photon doses of 8.0 and 8.5Gy and proton doses in excess of 2.5Gy.