1. A computer implemented method comprising: obtaining one or more first image regions of a first image of an eye, wherein each of the first image regions includes a view of a respective portion of vasculature of the eye; and until a score exceeds a threshold, progressively increasing a filter resolution and calculating the score based on the filter resolution, wherein calculating the score comprises: applying a plurality of filters having a first filter resolution to the first image regions to generate first filter output; deriving a plurality of first descriptors from the first filter output; comparing the first descriptors to second descriptors derived from second image regions of a second image of an eye, the second image regions comprising regions that are co-registered with the first image regions for corresponding descriptors in the plurality of first descriptors; determining, based on the comparing, that the score does not exceed the threshold; applying a plurality of filters having a second, higher filter resolution to the first image regions to generate second filter output; deriving a plurality of third descriptors from the second filter output; deriving fourth descriptors from the second image regions of the second image of the eye; and recalculating the score based on a combination of the first descriptors and third descriptors compared to a combination of the second descriptors and fourth descriptors.