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Direction associated with a particular retinal point. It is always perceived in the same direction if the light is received by the same retinal receptor. The capacity of a receptor to distinguish its excitation from that of its neighbours is referred to as local sign (or Lotze's local sign). This characteristic means that each retinal receptor has a unique oculocentric direction. See line of direction; oculocentre.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann