1. A method comprising: a) segmenting an optical coherence tomography (OCT) image to generate an OCT projection image for each of multiple biological layers; b) extracting from each of the generated OCT projection images a first set of features; c) extracting a second set of features from an input retinal fundus image; d) for each respective biological layer, registering the input retinal fundus image to the respective OCT projection image by matching at least some of the second set of features with corresponding ones of the first set of features; e) repeating elements a) through d) with changes to the input retinal fundus image; f) modelling how the changes to the input retinal fundus image are manifest at the correspondingly registered projection images; and g) storing in a computer readable memory a program that utilizes the modelling to generate estimated OCT projection images for the multiple biological layers from a given retinal fundus image.