Volumetric OCT image data processing

The invention relates to volumetric OCT image data processing. A method of processing C-scan data comprising a sequence of B-scans to an imaging target acquired by an OCT imaging system to generate correction data for compensating for axial displacement between B-scans in the sequence caused by relative movement of the OCT imaging system and the imaging target, the OCT imaging system has a relative motion that varies the distance between the OCT imaging system and the imaging target during acquisition of B-scans, the correction data being generated by: for each of a plurality of pairs of adjacent B-scans in the sequence, determining (S10) a respective indicator of axial displacement between respective representations of a common ocular feature in the adjacent B-scans; and determining (S20), according to a change in the determined indicator with the position of a corresponding adjacent B-scan pair in the sequence, a first frequency component of the change indicating the relative movement during acquisition of