1. An apparatus comprising: an acquiring unit configured to acquire a volume image of a retina; a detection unit configured to detect a center of a macula lutea by analyzing the volume image; a comparing unit configured to compare a thickness of the retina obtained from the volume image with a threshold value to obtain a difference as a degree of abnormality; a determining unit configured to determine a portion where the difference obtained by the comparing unit is larger than the difference of another portion on the retina, the portion determined by the determining unit being a different portion from the center of the macula lutea; and an acquiring position setting unit configured to set a single scan line for imaging and/or displaying a tomographic image of the retina, the single scan line passing through the portion determined by the determining unit and the center of the macula lutea.