1. A device to determine the contrast sensitivity of an individual's visual system through a series of tests in a measurement session, the device comprising: a means for producing real time digital images, corresponding to modulated visual stimuli; and a display means for presenting said images to an individual's eye; wherein said stimuli are configured in their spatial and temporal characteristics for each measurement session, and said stimuli are chosen in the cardinal directions of the color space, in which only one of the following mechanisms are able to respond to the stimulus: a non opponent or achromatic mechanism, a red-green opponency mechanism, and a blue-yellow opponency mechanism.