Horizontal Smooth Pursuit & Vertical Smooth Pursuit: these tests measure a user’s ability to track an object in a straight line (horizontally or vertically). This can provide further information about the degree of damage of the frontal white matter and the dorsolateral prefrontal cortex – areas that are critical to assess in concussion and TBI individuals (Bloom, 2013; Contreras et al., 2008; Contreras et al., 2011). Again, these tests determine if the user has a normal or an abnormal response.
Research has shown that vertical smooth pursuit is less robust than horizontal smooth pursuit (Collewijn & Tamminga, 1983; Ingester-Moati et al., 2009; Rottach et al., 1996). Scientists speculate this difference is due to a distinction between brain areas that process these movements, which develop at different rates, and because vertical eye movements are relatively less practiced in everyday routine. Moreover, it is believed that vertical smooth pursuit can be improved with practice to compensate for this difference.
In these tests, the user follows a target in each direction (horizontally or vertically from the midline) for approximately 10 seconds (back and forth to starting position). This is a digitized version of the Vestibular Ocular Motor Screening (VOMS) a clinical protocol used as part of a series of tests to assess for neurological deficits. The RightEye test for horizontal and vertical smooth pursuit is highly quantifiable, measurable, repeatable and specific.
Smooth Pursuit (%): eye movements that follow the target within a velocity range of the target, and are reported as a percentage of the test time. SP% refers to % of time spent in SP with acceptable distance and speed. 100% is perfect. Smooth Pursuit + Saccade + Fixation sum to 100%.
Saccade(s) (%): are fast eye movements that move the eyes from one point of interest to the next. They are calculated outside (above or below) the velocity range of the target and reported as a percentage of test time.
Fixation (%): is a stopping point of the eye that allows the user to see in detail, and are reported as a percentage of the test time. Fixation and Saccade % should be low.
Eye/Target Velocity Error (°/s): refers to how far the user’s eyes were away from the target (non-directional). This metric is calculated by subtracting the location of the stimuli and the user’s eyes at same sample time, and reported as degrees per second. Eye/Target Velocity Error refers to speed represented in degrees/second off target. A low number is better.
Vertical synchronization SPEM (0-1): refers to how far off on the Y plane (co-ordinate) the user’s eyes were during the test. Perfect synchronization is a score of 1.0.