 External beam radiotherapy XRT is second line therapy but is controversial, with some studies suggesting benefit in preventing onset of double vision or optic nerve compression while other studies suggest it has no benefit. Most proponents of XRT for TED believe that it is most effective early in the disease evolution. XRT has been shown to be a safe therapy with few side-effects, although retinopathy changes have developed in a small percentage of diabetics and its use is avoided for diabetics. 