1. A method of evaluating the neuroretinal rim of a patient, said method comprising the steps of: acquiring a 3D volume of intensity data using an optical coherence tomography (OCT) device, said volume including the optic nerve head; identifying the vitreoretinal interface (VRI) from the 3D data; defining an optic disc margin from the 3D data; determining a value corresponding to the minimum area of a 3D surface between the optic disc margin and the VRI; and displaying the value; wherein said step of determining a value corresponding to the minimum area of a 3D surface between the optic disc margin and the VRI comprises the steps of: dividing the optic disc margin into sectors; determining a value corresponding to the minimum area of a surface from the optic disc margin to the VRI for each sector; and summing the determined values.