1. An optical coherence tomography (OCT) system for collecting 3-D image data and displaying transverse slices of said image data on a graphical user interface said system including a processor comprising: a first image region for displaying a first transverse image slice; a second image region for displaying a second transverse image slice, the second transverse image slice being taken along an axis perpendicular to the first transverse image slice; a first indicator superimposed on the first transverse image slice in the first image region in a position that indicates the location within the 3-d image data of the second transverse image slice with respect to the first transverse image slice; and a user input device for moving the location of the first indicator in the first transverse image slice to a second position and in response thereto, a different second transverse image slice is displayed in the second image region, said different second transverse image slice corresponding to the second position of the first indicator.