A method for determining the axial length of an eye by optical coherence tomography (OCT), in which the alignment of the measuring instrument to the eye is monitored to enable reliable determination of the axial length of the eye. B-scans are carried out following alignment from which scans of the retinal tissue structures are detected to determine the axial lengths, which are then used in the detection of the fovea in order to monitor alignment. The axial lengths determined from the B-scans are then confirmed or corrected and output depending, on the determined position of the fovea or the lateral distance thereof from the optical axis of the measuring instrument. The method is particularly suitable for OCT methods in which the axial length is determined on the basis of an A-scan along the axial dimension of the eye.
