1. A method for operating an image display apparatus, comprising: receiving motion information from a remote controller; determining a movement of the remote controller based on the motion information; calculating coordinates of a pointer; receiving an image including at least one three-dimensional (3D) object; generating an on-screen display (OSD) signal, including the pointer; converting the OSD signal to a 3D OSD signal; calculating a depth value of the at least one 3D object and a 3D pointer corresponding to the pointer; changing at least one of sharpness and brightness of pixels corresponding to the at least one 3D and the 3D pointer object according to the depth value and generating an output image including the changed at least one 3D object and the 3D pointer; and displaying the output image, wherein the calculating step comprises: receiving a left-eye image data and a right eye image data of the 3D object; calculating edges of the left-eye image data and the right eye image data; detecting starting pixels and ending pixels of the edges; calculating a shift value between the starting pixels of the edges detected from the left-eye image data and right-eye image data, and a shift value between the ending pixels of the edges detected from the left-eye image data and right-eye image data; calculating a disparity between the left-eye image data and right-eye image data of the 3D object using the edge shift values; and calculating the depth value of the 3D object using the calculated disparity, and wherein the changing step changes the at least one of the sharpness and brightness of pixels corresponding to the 3D object and the pointer according to the depth value on a block basis using an image information table, wherein at least one of sharpness and brightness of pixels corresponding to the 3D OSD is changed according to depth value of the 3D OSD, and wherein the 3D pointer is shifted by the movement of the remote controller.