An ophthalmological patient interface device (27), for application onto an eye (3) during treatment of the eye (3), comprises a coupling part (21) for attaching mechanically the ophthalmological patient interface device (27) to an optical projection system (20) of an ophthalmological apparatus (1), and a fastening device (271) for fastening the ophthalmological patient interface device (27) to the eye (3). The ophthalmological patient interface device (27) further comprises a mirror system (275) arranged downstream from the optical projection system (20), when the ophthalmological patient interface device (27) is attached mechanically to the optical projection system (20), and having at least one mirroring surface arranged at an angle with respect to a projection axis of the optical projection system (20), such that a laser beam (L3) projected by the optical projection system (20) is deflected by the mirror system (275).
