Comparative monocular contributions to brightness in relation to abnormal stereothreshold

This study was designed to compare brightness contributions of the two monocular inputs to the binocular visual system at three different levels of luminance adaptation in two groups of 15 subjects each. The only known difference between these groups was stereothreshold, 50 to 70 sec arc in one group vs. 40 sec arc or less in the other group. The group with elevated threshold was found to have a significantly larger average difference (13.5%, p less than 0.002) in monocular brightness contributions, between the right and left eyes, when compared to the group with lower stereothresholds (4% mismatch). The results also indicate that neither group showed a significant variation in mismatch as adapting luminance was altered by a factor of four times (0.6 log units). Finally, no clear relation was found between eye dominance and the eye requiring higher illuminance to attain the dichoptic brightness match.