a and 55 a are located along an optical axis of the eye behind i e downstream of the iris without limiting the field of view of the eye for example r 1 may be chosen to be greater or equal to 3 mm and r 2 may be chosen to be smaller or equal to 6 mm the intraocular lens 19 a may be used for an improved cataract surgery by using the oct system 1 which is illustrated in fig1 thereby the high sensitivity of the oct system 1 may be used for imaging marks 54 a 55 a of the implanted intraocular lens 19 a which is located in the capsular bag 17 behind the iris 14 whereby it is possible to determine the exact position of the intraocular lens 19 a within the capsular bag 17 an inaccurate position or inaccurate orientation of the implanted intraocular lens 19 a may be determined for example a tilt of the optical axis 51 a of the intraocular lens 19 a in relation to an optical axis of the eye or an inaccurate azimuthal orientation of the intraocular lens 19 a relative to the optical axis 51 a in case the optical element 50 a.