Radiation retinopathy (Fig. 6.5) is a well-documented consequence of radiation treatment. It is characterized by specific examination findings, including mi-croaneurysms, hard exudates, cotton-wool spots, optic disc swelling, vascular occlusion, hemorrhages and neovascularization. These changes are clinically indistinguishable from retinal changes due to diabetes. Radiation retinopathy can develop as soon as 3 weeks, and as late as 15 years, following RT, although, typically, it occurs between 1 and 3 years.
Although as little as 15 Gy of external beam radiation has led to signs of retinopathy, 30-60 Gy are usually required. In the authors' experience, fewer than 5 % of children treated with external beam radiation for retinoblastoma develop radiation retinopathy. 50 Gy is regarded as the threshold for the development of retinopathy following radioactive plaque exposure. Either a history of diabetes mellitus or concurrent treatment with chemotherapy is believed to increase susceptibility to radiation retinopathy [3,27].
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