A computer-implemented method of processing functional OCT image data, which has been acquired by an OCT imaging device scanning a retina of a subject while the retina is being repeatedly stimulated by a light stimulus, to generate an indication of a response of the retina to the light stimulus, the method comprising: receiving, as the functional OCT image data: OCT image data that has been generated by the OCT imaging device repeatedly scanning a scanned region of the retina over a time period; and stimulus data defining a sequence of stimulus indicators (s 1, s 2, s 3) each being a respective value which is indicative of a stimulation of the retina by the light stimulus in a respective time interval of a sequence of time intervals that spans the time period; and calculating a rolling window correlation between a sequence of B-scans that is based on the OCT image data and stimulus indicators (s 1, s 2, s 3) in the sequence of stimulus indicators by: calculating (S20-1), for each stimulus indicator (s 1; s 2; s 3), a product of the stimulus indicator and a respective windowed portion of the sequence of B-scans comprising a plurality of B-scans (600-1; 600-2) which includes a B-scan that is based on a portion of the OCT image data generated while the retina was being stimulated in accordance with the stimulus indicator (s 1; s 2; s 3); and combining the calculated products to generate the indication of the response of the retina to the light stimulus. receiving, as the functional OCT image data: OCT image data that has been generated by the OCT imaging device repeatedly scanning a scanned region of the retina over a time period; and stimulus data defining a sequence of stimulus indicators (s 1, s 2, s 3) each being a respective value which is indicative of a stimulation of the retina by the light stimulus in a respective time interval of a sequence of time intervals that spans the time period; and OCT image data that has been generated by the OCT imaging device repeatedly scanning a scanned region of the retina over a time period; and stimulus data defining a sequence of stimulus indicators (s 1, s 2, s 3) each being a respective value which is indicative of a stimulation of the retina by the light stimulus in a respective time interval of a sequence of time intervals that spans the time period; and calculating a rolling window correlation between a sequence of B-scans that is based on the OCT image data and stimulus indicators (s 1, s 2, s 3) in the sequence of stimulus indicators by: calculating (S20-1), for each stimulus indicator (s 1; s 2; s 3), a product of the stimulus indicator and a respective windowed portion of the sequence of B-scans comprising a plurality of B-scans (600-1; 600-2) which includes a B-scan that is based on a portion of the OCT image data generated while the retina was being stimulated in accordance with the stimulus indicator (s 1; s 2; s 3); and combining the calculated products to generate the indication of the response of the retina to the light stimulus. calculating (S20-1), for each stimulus indicator (s 1; s 2; s 3), a product of the stimulus indicator and a respective windowed portion of the sequence of B-scans comprising a plurality of B-scans (600-1; 600-2) which includes a B-scan that is based on a portion of the OCT image data generated while the retina was being stimulated in accordance with the stimulus indicator (s 1; s 2; s 3); and combining the calculated products to generate the indication of the response of the retina to the light stimulus.