Abstract
Smooth pursuit eye movements (SPEM) are continuous eye movements which occur in response to a moving target. SPEM can be observed as a slow rotation of the eyes keeping the object of pursuit in fovea. SPEM occur in response to following moving objects and cannot be initiated voluntarily [1]. To maintain smooth pursuit, the brain must predict and calculate appropriate eye movements based on observed speed and direction of a target to ensure a stable image. SPEM cannot be maintained if the speed of the target exceeds 30 degrees/s [1, 2]. As the speed of the object increases, the smooth movements will be interrupted by catch up punctuated by saccades [1]. Smooth pursuit are quantified by the gain (how well the eyes follow the target in speed) and phase (distance to the target during pursuit)[3]. Testing of SPEM ability is often included in visual exams and thought to provide information on sudden or developmental damage to the oculomotor system or the controlling functions such as attention. However, very little normative data exists and assessment guidelines on execution, scoring and interpretation of SPEM are almost non-existing. This study targeted three challenges in relation to this: 1) that hand-held movement of an object may be too fast, unsteady or unpredictable for activating SPEM, 2) the lack of normative data and 3) improved quantification of activities during a SPEM task. 96 children were tested three times in our smooth pursuit paradigm. Software to capture, quantify and analyze the data was developed. Apart from gain and phase, the quantification includes data on backup, catchup and distractor saccades, eye dominance as well as dividing period of smooth pursuit into pursuit on and off target. The quantification parameters has been tested subsequently and been shown to correlate nicely with appropriate measures of visual attention.
Acknowledgement: The Synoptik-foundation and the Rockwell Foundation