Accommodative and fusional components of fixation disparity.

Traditional measurements of fixation disparity, like other binocular measurements, confound influences from both blur-driven and disparity-driven components. Measuring fixation disparity with accommodation open-loop eliminates accommodative interactions, and results show fixation disparity is reduced to about half the value observed normally for high levels of forced vergence. Thus fixation disparity curves are shaped by both accommodative and fusional vergence processes.