A method and an optical arrangement for removing contamination on optical surfaces (26), which are arranged in a vacuum environment in an optical arrangement, preferably in a projection exposure apparatus (1) for EUV lithography. The method includes generating a residual gas atmosphere containing molecular hydrogen (18) and at least one inert gas (17) in the vacuum environment, generating inert gas ions (21) by ionization of the inert gas (17), preferably with EUV radiation (20), and generating atomic hydrogen (27) by acceleration of the inert gas ions (21) in the residual gas atmosphere, to remove the contamination.