Radiation therapy: posterior segment complications.

Therapeutic radiation to the posterior segment of the eye is a common option for posterior segment tumors. Such tumors are often malignant, but sometimes, benign neoplasms are treated with ionizing radiation. Also, non-neoplastic intraocular lesions like wet age-related macular degeneration may be treated with radiotherapy. Orbital disease, both neoplastic lesions like optic nerve sheath meningioma and non-neoplastic entities like Graves' ophthalmopathy may be treated with radiotherapy and this may include radiation of the optic nerve and posterior segment of the eye. Occasionally, radiotherapy of extraocular malignant disease, involving, e.g. the paranasal sinuses, may cause significant radiation damage to the eye. Complications after radiation to the posterior segment of the eye are largely related to the radiation dose to the posterior segment. The amount of irradiated volume of normal tissue and fractionation are also important for the development of radiation complications to the posterior segment. Radiation retinopathy is the most common complication of the posterior segment, but radiation optic neuropathy also occurs frequently. Radiation scleral necrosis is less frequent probably due to the radioresistance of the scleral collagen. These complications have the potential to cause blindness (radiation retinopathy and optic neuropathy) or enucleation of the eye (scleral necrosis). Although numerous treatments have been advocated, management of radiation-induced damage remains controversial. Efficacy for any treatment still needs to be proven and, if possible, the best option by far is to minimize radiation changes to normal tissue.