Effect of stimulus type on the eye movements of children.
OBJECTIVE
The authors investigated whether pictures elicit superior response rates and eye movement dynamics on saccade and pursuit tasks than do dots or spots of light and whether the need for more interesting stimuli is age dependent.


METHODS
Using video eye tracking, horizontal eye movements were investigated in children and adults using dots and small colored pictures as stimuli. Saccade data were obtained from 61 people and pursuit data from 53 people, ages 3 to 30 years, with no known ocular, ocular motor, neurologic, or systemic disease. Saccadic stimuli were randomly presented in steps ranging in size from 5° to 30°. Pursuits at four velocities (5°/s, 10°/s, 20°/s, and 30°/s) were tested using step ramp stimuli.


RESULTS
Picture targets result in age-dependent improvements in ocular motor responses compared with dots. With the exception of saccadic accuracy, the youngest children are most affected by the type of target. Adults are affected very little. For pictures, saccadic response rates (t((60)) = 4.30, P < 0.001), saccadic peak velocities (t((60)) = 2.24, P = 0.03), saccadic accuracy (t((59)) = 2.34, P = 0.02), and closed-loop pursuit gains (F((3,50)) = 2.86, P = 0.046) are higher. Saccadic error rates (t((60)) = 3.91, P < 0.001) and saccadic latencies (t((59)) = 9.5, P < 0.001) are lower with pictures.


CONCLUSIONS
Stimulus characteristics can affect response rates and eye movement dynamics, particularly in young children. To avoid underestimation of eye movement performance in young children, it is important to use meaningful targets. Furthermore, when comparing the ocular motor performance of children across studies one must consider the type of stimuli used.
Irving
Elizabeth L
EL
School of Optometry, University of Waterloo, Waterloo, Canada. elirving@sciborg.uwaterloo.ca
González
Esther G
EG
Lillakas
Linda
L
Wareham
Jonathan
J
McCarthy
Tara
T
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D011597:Psychomotor Performance; D011698:Pursuit, Smooth / Q000502:physiology*; D012438:Saccades / Q000502:physiology*; D014794:Visual Fields; D055815:Young Adult