Radiation optic neuropathy is a consequence of highdose radiation therapy delivered to the region of optic nerve and/or chiasm, which often presents abruptly in a manner that mimics acute retrobulbar optic neuritis. The loss of vision is usually profound and there is no effective therapy to reverse the process, once it has begun.
An interval of 9 to 12 months (or more) after radiation therapy is the usual temporal sequence, and the optic disc is initially normal in appearance (hence the similarity to the presentation of demyelinating optic neuritis). The pathogenesis is thought to be ischemic, caused by loss of capillary endothelial cells that cease growing and die out, leading to expanding areas of capillary dropout and radiation necrosis within the nerve. High-dose corticosteroid therapy and hyperbaric oxygen therapy have been tried, but with no success. The prognosis is usually grim (see Chap. 23).
Fig. 8.21. Optic disc appearance in a patient with an infiltrating optic neuropathy and chronic myeloic leukemia
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