A method of processing C-scan data, which comprises a sequence of B-scans of an imaging target acquired by an OCT imaging system, to generate correction data for compensating for axial displacements between B-scans in the sequence caused by a relative motion of the OCT imaging system and the imaging target that varies a distance therebetween during acquisition of the B-scans, the correction data being generated by determining, for each pair of adjacent B-scans of a plurality of pairs of adjacent B-scans in the sequence, a respective indicator of an axial shift between respective representations of a common ocular feature in the adjacent B-scans; and determining, from a variation of the determined indicators with locations of the corresponding pairs of adjacent B-scans in the sequence, a first frequency component of the variation which is indicative of the relative motion during acquisition of the B-scans.