Posterior ocular abnormalities after irradiation for retinoblastoma: a histopathological study

Radiation-induced ocular lesions in the posterior eye and orbit were investigated in 33 surgical specimens of patients with retinoblastoma. The eyes were obtained from children 7 months to 6 years of age. Seventeen eyes were irradiated; 16 eyes had not received irradiation and served as controls. The majority of the irradiated eyes were treated with 6000 rads of external beam radiation. They were removed at a mean of 23 months after radiotherapy. All specimens were examined simultaneously by 2 observers without knowledge of treatment and analysed for the presence or absence of 15 lesions. The most consistent lesions in the irradiated eyes were abnormalities of the retinal vessels (11 of 17 eyes) and striking changes in the ciliary arteries (13 of 17 eyes). The retinal vessels showed thickening of the wall, often caused by deposition of fibrillary material, sometimes with fibrin deposits. The most consistent lesion was myointimal proliferation with narrowing of the ciliary arteries. Lesions of the central retinal artery were less common but occurred only in irradiated patients.