In search of a treatment for radiation-induced optic neuropathy.

Radiation-induced optic neuropathy (RON) is an iatrogenic complication that causes severe, irreversible vision loss in one or both eyes within the months to years following radiation therapy. Posterior RON is a rare but devastating toxicity of radiation applied to the visual pathways to treat paranasal sinus and skull base tumors. Anterior RON is an unavoidable consequence of proton beam irradiation or ophthalmic plaque treatment of orbital, choroidal, or retinal tumors. Various treatments aimed at stabilizing and ideally reversing vision loss have been investigated but only in small cases series. Systemic corticosteroids and anticoagulants, which are moderately effective when used for cerebral radiation necrosis, have shown no signs of benefit for RON. Hyperbaric oxygen therapy may promote short-term, partial recovery of vision in select patients, especially at partial pressures of at least 2.4 atm and when administered early after symptom onset. Reversal of visual deficits through treatment with systemic bevacizumab has been reported, but until controlled studies are performed, the side effect profile of stroke and myocardial infarction should limit its use in a population with predisposing cardiovascular risk factors. Intravitreal bevacizumab has shown promising results in patients with anterior RON, but repeated, long-term injections are required for sustained effect. As no intervention has been clearly shown to halt or reverse vision loss, larger prospective studies are needed to validate observed benefits for any of the treatments that have been described.