Thyroid-associated orbitopathy (TAO) is an inflammatory autoimmune disorder.The mast serious complication of TAO is dysthyroid optic neuropathy (DON),which can lead to permanent vision loss because of volume expansion in the orbital apex.Orbital radiation therapy (ORT) is an anti-inflammatory treatment used in the treatment of active TAO.Clinical studies support radiotherapy as having a modest effect on DON,and early radiotherapy may protect against disease progression to DON.Current studies suggest that radiotherapy is generally safe.However,risks still exist in some cases.The possible effects of radiotherapy on TAO,especially complicated with DON,are reviewed.The effects of radiotherapy on DON are not completely known,and evidence from standardized,prospective,and multicenter clinical trials is still lacking.