Disclosed are method and apparatus for mapping retinal thickness values to a movable measurement grid. A three-dimensional volume dataset acquired from three-dimensional optical coherence tomography is registered to a fundus image by rendering a two-dimensional composite image from the three-dimensional volume dataset and superimposing characteristic features in the two-dimensional composite image upon corresponding characteristic features in the fundus image. A measurement grid is displayed on the two-dimensional composite image. The measurement grid is moved to a region of interest, and retinal thickness values in the region of interest are mapped to sectors within the measurement grid.