A conventional method of detecting a gaze point may not be able to appropriately support diagnosis depending on a diagnosis image presented to a subject, and a more accurate detection method has been sought. To improve accuracy of diagnosis, in a control device that displays, on a display, a diagnosis image that is a combination of a natural image and a pattern image, the control device includes an output controller that displays a first diagnosis image on the display, and displays a second diagnosis image in which a portion of the natural image and the pattern image are similar, compared with the first diagnosis image, on the display, after displaying the first diagnosis image.
