A computer-implemented method of rendering optical coherence tomography, OCT, retinal image data, which has been acquired by an OCT scanner scanning a retina of an eye over a range of scan locations, wherein each of the scan locations is associated with a respective coordinate in a first coordinate system, and each pixel of the rendered OCT retinal image data is associated with a respective coordinate in a second coordinate system that is different from the first coordinate system, the method comprising: receiving, via a communication module, the OCT retinal image data acquired by the OCT scanner; and processing a pixel array using the received OCT retinal image data to generate the rendered OCT retinal image data by: determining, via a coordinate-determining module, for each pixel of the pixel array, a respective coordinate in the first coordinate system using a transformation from coordinates in the second coordinate system to coordinates in the first coordinate system; and characterized in that the method further comprises the step of calculating, via an interpolation module, values of the pixels of the pixel array by using the determined coordinates in the first coordinate system to interpolate between values of pixels of the received OCT retinal image data, wherein the respective coordinate in the first coordinate system for each pixel of the pixel array is determined using: a first mapping for converting the coordinate of the pixel of the pixel array in the second coordinate system to a coordinate in a first real-world coordinate system; a second mapping for converting the coordinate of the pixel of the pixel array in the first real-world coordinate system to a coordinate in a second real-world coordinate system; a third mapping for converting the coordinate of the pixel of the pixel array in the second real-world coordinate system to a set of OCT scan parameter values indicative of a location within the scan performed by the OCT scanner; and a fourth mapping for converting the set of OCT scan parameter values to the coordinate of the pixel of the pixel array in the first coordinate system. receiving, via a communication module, the OCT retinal image data acquired by the OCT scanner; and processing a pixel array using the received OCT retinal image data to generate the rendered OCT retinal image data by: determining, via a coordinate-determining module, for each pixel of the pixel array, a respective coordinate in the first coordinate system using a transformation from coordinates in the second coordinate system to coordinates in the first coordinate system; and characterized in that the method further comprises the step of calculating, via an interpolation module, values of the pixels of the pixel array by using the determined coordinates in the first coordinate system to interpolate between values of pixels of the received OCT retinal image data, determining, via a coordinate-determining module, for each pixel of the pixel array, a respective coordinate in the first coordinate system using a transformation from coordinates in the second coordinate system to coordinates in the first coordinate system; and characterized in that the method further comprises the step of calculating, via an interpolation module, values of the pixels of the pixel array by using the determined coordinates in the first coordinate system to interpolate between values of pixels of the received OCT retinal image data, wherein the respective coordinate in the first coordinate system for each pixel of the pixel array is determined using: a first mapping for converting the coordinate of the pixel of the pixel array in the second coordinate system to a coordinate in a first real-world coordinate system; a second mapping for converting the coordinate of the pixel of the pixel array in the first real-world coordinate system to a coordinate in a second real-world coordinate system; a third mapping for converting the coordinate of the pixel of the pixel array in the second real-world coordinate system to a set of OCT scan parameter values indicative of a location within the scan performed by the OCT scanner; and a fourth mapping for converting the set of OCT scan parameter values to the coordinate of the pixel of the pixel array in the first coordinate system. a first mapping for converting the coordinate of the pixel of the pixel array in the second coordinate system to a coordinate in a first real-world coordinate system; a second mapping for converting the coordinate of the pixel of the pixel array in the first real-world coordinate system to a coordinate in a second real-world coordinate system; a third mapping for converting the coordinate of the pixel of the pixel array in the second real-world coordinate system to a set of OCT scan parameter values indicative of a location within the scan performed by the OCT scanner; and a fourth mapping for converting the set of OCT scan parameter values to the coordinate of the pixel of the pixel array in the first coordinate system.