Fig. 4. Binocular eye traces from subject 3, plotted separately for vertical (top) and
horizontal (bottom) eye motion. Left eye motion is plotted in blue, right eye in red,
and the difference (vergence movement) is plotted in green. The inset shows the
standard deviation of the difference signal in arc minutes. The fine magenta line
indicates the section of the records used to calculate the SD, with the last 1.5 s
omitted due to tracking loss of the right eye. The difference between the left and
right eye vertical traces had an SD of just under 1 arc min.