Most traditional tests for binocular coordination (e. g., fixation disparity)
examine the eyes when the visual object to be observed does not move. We extent
this conventional approach in two ways:
- At visual work, one never observers a target for a longer period of time,
rather the eyes are always in move. The gaze direction is changed with fast
saccadic eye movements, when we fixate one target after the other on a computer
screen or one word after the next during reading. The eyes keep fixation on
a target only as short as 0,2 seconds during reading. We measure the coordination
of the two eyes during this fast eye movement process.
- The viewing distance from the eyes to the visual target is rarely constant
over time, rather changes due to head movements or gaze changes to targets
at different distances. This requires to adjust the angle between the visual
axes of the two eyes, known as the vergence angle. Therefore, we investigate
the dynamics of vergence eye movements, stimulated by disparity or viewing
distance.
In these dynamic viewing conditions, we measure the movements of the two eyes
with the EyeLink II recording system and analyse the binocular coordination
with respect to individual differences in eye movement patterns.
Jainta S, Hoormann J, Jaschinski W: Objective and subjective measures of vergence
step responses.Vision Res 47: 3238-3246 (2007)