To protect tissue in the treatment of an eye (3) with a focused pulsed laser beam (21) generated by a laser system (2), e.g. a femtolaser system, operating data which define an operating area operated on by the focus (F) of the laser beam (21) during the treatment are acquired in a device (1). The device (1) comprises a processing module (14) for providing control data for the laser system (2) on the basis of the operating data and taking into consideration the light propagation in the eye. The control data limit the time of the treatment by the focus (F) at positions within the operating area in each case in such a manner that tissue damage resulting from the treatment by the laser beam (21) is essentially prevented in eye structures located outside the operating area. In particular, the control data determine movements of the focus (F) within the operating area and/or the activity of the laser beam (21) in such a manner that the mean irradiation intensity is reduced and the maximum temperatures in the tissue of eye structures located outside the operating area, particularly in the iris and the retina, are reduced.