A method of processing functional OCT image data, acquired by an OCT scanner scanning a retina that is being repeatedly stimulated by a light stimulus, to obtain a response of the retina to the light stimulus, comprising: receiving OCT image data generated by the OCT scanner repeatedly scanning the retina over a time period, and a sequence of stimulus indicators each indicative of a stimulation of the retina by the light stimulus in a respective time interval of a sequence of time intervals spanning the time period; calculating, for each stimulus indicator, a product of the stimulus indicator and a respective windowed portion of the sequence of B-scans comprising a B-scan based on a portion of the OCT image data generated while the retina was being stimulated in accordance with the stimulus indicator; and combining the calculated products to generate the indication of the response.