A method performed in at least one processor for pre-processing visualizable data to be manipulatable in response to user input produced based on gaze data registered for a subject regarding a display and/or tactile input registered on the display, the method comprising the steps of: obtaining visualizable data (D in) representing a scene including at least one object (110, 120, 130, 310, 320, 330, 340, 350, 510, 610), the visualizable data (D in) describing the scene as seen from a position, determining a first measure representing an extension of the object (110, 510) in a smallest dimension, and a second measure representing an extension of the object (110, 410) in a largest dimension as seen from the position, calculating an object aspect ratio representing a relationship between the first and second measures (L1; L2), characterized by: assigning, based on the object aspect ratio, a selection margin (M, M51, M1, M2, M3, M4, M5, M6) to the object (110, 120, 130, 310, 320, 330, 340, 350, 510, 610), the selection margin designating a zone outside of the object within which zone the object is validly selectable for manipulation in addition to an area (A 11) of the object shown towards a view thereof as seen from the position, wherein the selection margin (M, M51, M1, M2, M3, M4, M5, M6) is assigned such that an extension of the zone in at least one direction outside of the object depends on the object aspect ratio according to an expression: E = KR − x, where E is the extension of the zone in the at least one direction, K is a constant larger than zero, R is the object aspect ratio, smaller than or equal to one, and x is a constant larger than or equal to one. obtaining visualizable data (D in) representing a scene including at least one object (110, 120, 130, 310, 320, 330, 340, 350, 510, 610), the visualizable data (D in) describing the scene as seen from a position, determining a first measure representing an extension of the object (110, 510) in a smallest dimension, and a second measure representing an extension of the object (110, 410) in a largest dimension as seen from the position, calculating an object aspect ratio representing a relationship between the first and second measures (L1; L2), characterized by: assigning, based on the object aspect ratio, a selection margin (M, M51, M1, M2, M3, M4, M5, M6) to the object (110, 120, 130, 310, 320, 330, 340, 350, 510, 610), the selection margin designating a zone outside of the object within which zone the object is validly selectable for manipulation in addition to an area (A 11) of the object shown towards a view thereof as seen from the position, wherein the selection margin (M, M51, M1, M2, M3, M4, M5, M6) is assigned such that an extension of the zone in at least one direction outside of the object depends on the object aspect ratio according to an expression: E = KR − x, where E is the extension of the zone in the at least one direction, K is a constant larger than zero, R is the object aspect ratio, smaller than or equal to one, and x is a constant larger than or equal to one. assigning, based on the object aspect ratio, a selection margin (M, M51, M1, M2, M3, M4, M5, M6) to the object (110, 120, 130, 310, 320, 330, 340, 350, 510, 610), the selection margin designating a zone outside of the object within which zone the object is validly selectable for manipulation in addition to an area (A 11) of the object shown towards a view thereof as seen from the position, wherein the selection margin (M, M51, M1, M2, M3, M4, M5, M6) is assigned such that an extension of the zone in at least one direction outside of the object depends on the object aspect ratio according to an expression: E = KR − x, where E is the extension of the zone in the at least one direction, K is a constant larger than zero, R is the object aspect ratio, smaller than or equal to one, and x is a constant larger than or equal to one. E is the extension of the zone in the at least one direction, K is a constant larger than zero, R is the object aspect ratio, smaller than or equal to one, and x is a constant larger than or equal to one.