An ophthalmic device (1) for treating eye tissue (7) comprises a light source (2) for generating laser pulses (P), a light projector (60) for focused projection of the laser pulses (P) into the eye tissue (7) and an interferometric measurement system (3) for measuring eye structures. The ophthalmic device (1) moreover comprises an optical element (32) which is movable in relation to the aforementioned light source (2) and provided for preventing a change in the path length difference between measurement arm (30a) and reference arm (30b) of the interferometric measurement system (3) as a result of a change (Δx) in the length of the light-transmission path (L) caused by a movement of the light projector (60) relative to the aforementioned light source (2). The interferometric measurement system (3) enables a flexible measurement of the eye structures before, during and after the treatment, wherein measurement errors in the interferometric measurement system (3) as a result of length changes in the light-transmission path (L) are avoided, which are caused by movements of the light projector (60) relative to the aforementioned light source (2).
