A method of determining a measurement of at least one cell type in an eye, comprising (i) obtaining a map of the cell type in the eye, (ii) obtaining a representation of the retina of the eye, (iii) matching the eye cell type map to the representation of the retina of the eye, (iv) defining a region of interest on the representation of the retina of the eye, (v) calculating a size of the region of interest on the representation of the retina of the eye, (vi) using the matched eye cell type map and the size of the region of interest to determine a measure of the cell type in the region of interest of the retina of the eye.