of a lens for an eye the lens 4 may be for example a contact lens or an intra ocular lens comparably to the embodiment of fig2 the embodiment of fig3 comprises radiation sources 14 1 14 n which emit radiation of different wavelengths the explanations given in this connection with reference to fig2 apply correspondingly here this also applies to the switching device 38 containing radiation from the radiation sources 14 test radiation 12 emitted by the switching device 38 is fed to the lens 4 directly or via optics arranged between the switching device 38 and the lens 4 which in fig3 comprise an exit lens l and a lens l s for beam expansion for representational purposes only test radiation 20 resulting from interaction of the test radiation 12 with the lens 4 is fed to a sensor device 26 via optics comprising as an example lenses l and a cylindrical compensator zk in particular for pre compensation and an aperture bl with a lens l connected downstream the sensor device 26 is substantially comparable to the sensor devices 26 of fig1 and 2 this applies in particular to the scanning rates at which the sensor device 26 is operated.