1. A computer-implemented method comprising: obtaining one or more image regions from a first image of an eye, wherein each of the image regions includes a view of a respective portion of vasculature of the eye external to a corneal limbus boundary of the eye; applying a convolutional filter to each of the image regions at a plurality of different orientations to generate a plurality of respective filtered images for the image region; generating a respective descriptor for each of the image regions based on, at least, phases of image data elements in the respective filtered images for the image region wherein generating comprises thresholding image data elements of the respective filter images for the image region based on phase values of the image data elements to create respective thresholded images for the image region by setting image data elements having phase values above a first threshold or below a second threshold to a first value, and setting image data elements having phase values in the range of the first threshold to the second threshold to a different second value; and determining a score based on the generated descriptors and based on one or more descriptors associated with a second image of eye vasculature.