About

Horizontal & Vertical Saccades: “…are fast (usually between 300 and 600°/s), tandem, conjugate movements which rapidly shift the fovea to a new target” (Alvarez et al, 2010; Bieg et al., 2015; Burke & Barnes, 2006). The ability to execute saccades degrades, as with smooth pursuit, with mTBI often despite no oculomotor or visuomotor deficits on standard clinical examination. Furthermore, the latency of a saccade has been linked to over 30 neurological deficits (Crawford et al., 2015; Crutcher et al., 2009; Shakespeare et al., 2015). These findings indicate that abnormalities of saccades and upper-limb visuomotor function following closed head injuries may provide sensitive markers of cerebral dysfunction, independent of psychometric status. Sensitive computerized motor testing and eye tracking are warranted to help predict and track recovery after a neurological disorder is identified. Additional evidence exists that saccades may be used to predict recovery (Heitger et al.., 2008) and be biomarkers for over 30 neurological disorders (Samadani et al.., 2015; Heitger et al.., 2008a).

Vertical saccades are slower than horizontal saccades, with downward saccades being the slowest. The rightward saccade is faster than the leftward saccade. Oblique saccades, or saccades executed at an angle, are a result of the summation of forces of the horizontal and vertical systems, can be faster than either purely horizontal or vertical saccades of the sample amplitude. Horizontal and vertical saccades use different extraocular motor neurons that generate these movements. Therefore, RightEye measures saccades in both directions providing a complete mapping of extraocular motor neurons to help be more specific in determining areas of injury (Holmqvist & Nystrom, 2011; Leigh & Zee, 2006; Bahill & Stark, 1975).

RightEye protocols for saccades follow the VOMS clinical standard as well as the standard neurological clinical evaluations. RightEye saccade tests not only count the number of saccades within a period of time, but also report the accuracy of the stopping point (fixation) between saccadic eye movements.

Metrics

Saccade(s) (%): are fast eye movements that cross from the left to right of the side of the screen or from the right to the left side of the screen. Saccades are tallied throughout the duration of the test and reported as the total number of saccades. Saccade (#) refers to number of saccades tallied for a single test. 1 saccade is from one black dot to the other. Smooth Pursuit + Saccade + Fixation sum to 100%.

Fixation (%): are stopping points or about-turn of the user’s gaze. Fixations are tallied throughout the duration of the test and reported as the total number of fixations. Fixation (#) refers to number of times user stops moving their eye.

On-Target (9mm, #): is a tally of x, y coordinates within the left and right targets. These “hits” are tallied across the length of the test  and are reported as a total number of target hits. On-Target refers to accuracy of the saccade and proximity of eye gaze point to the dot when fixating.

Bandwidth 2 Overshot Target (9-18 mm; #): is a tally of x, y coordinates that appear  beyond  the targets to the far left and far right side. These “hits” are tallied across the length of the test  and are reported as a total number  of target  overshot. Bandwidth refers to the distance from eye gaze point to dot.

Bandwidth 2 Undershot Target (9-18 mm, #): are a tally of x, y coordinates that appear  closer to the center of the screen,  inside the targets to the inner left and inner right side of the targets. These “hits” are tallied across the length of the test  (10 seconds) and are reported as a total number  of target undershot.

Bandwidth 3 Overshot Target (18-36 mm, #): are a tally of x, y coordinates that appear beyond the targets to the far left and far right side of the targets. These “hits” are tallied across the length of the test  (10 seconds) and are reported as a total number of target overshot.

Bandwidth 3 Undershot Target (18-36 mm, #): are a tally of x, y coordinates that appear closer to the center of the screen,  inside the targets to the inner left and inner right side of the targets. These “hits” are tallied across the length of the test (10 seconds) and are reported as a total number of target  undershot.

Missed (>36 mm, #): A target miss is recorded when no target is hit and the user has passed the center of the screen in the direction of the target.

Saccadic Efficiency: refers to the average distance the users’ saccade is from the ideal pathway.

Saccadic Targeting: refers to the distance each “hit” or fixation was compared to the ideal target. 

Saccadic Speed: refers to the average velocity made by the saccades across the test time.

S/A Ratio: Speed divided by accuracy or velocity divided by saccadic targeting, helps provide context as to the speed-accuracy trade-off. Did the user have a bias toward being quick or accurate?

Saccadic Recovery: refers to the difference in the path taken before and after a fixation. A wide, looping path is inefficient. A narrow path is ideal.

Saccadic Variance: is the spread or variability in the saccadic pathways.