It has been generally assumed that the two eyes of a normal observer provide equal inputs to the visual cortex for the sensation of brightness, since artificially produced unequal inputs result in distortion of binocular perception. This study measures the comparative brightness contributions of the two monocular inputs to the visual system at three different levels of luminance adaptation. Two groups of fifteen subjects each were evaluated, with the only known difference between these groups being stereothreshold (50-70 arcsec vs 40 arcsec or less). The group with elevated threshold was found to have a significantly larger mismatch in monocular brightness contributions (between the right and left eyes) when compared to the group with normal stereoacuity. The results also indicate that neither group showed a significant variation in mismatch as adapting luminance was altered by a factor of four .(0.6 log units). Finally, there was found to be no clear relation between eye dominance and the eye requiring higher illuminance to attain the dichoptic brightness match.
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