Abstract
Introduction: Eye-hand coordination is important for normal child development and early academic success. We have previously shown manual dexterity deficits on a standardized clinical test in children with deprivation amblyopia due to a dense unilateral cataract (Kelly et al., 2019). Here, we investigate reach and saccade kinematics during visually-guided reaching to determine the contribution of eye movements to fine motor deficits observed in children with deprivation amblyopia. Methods: Thirteen children (age 7-15 years) with deprivation amblyopia and 23 age-similar controls completed a visually-guided reaching task during binocular viewing. Hand movements (Leap Motion Controller) and eye movements (EyeLink 1000) were recorded simultaneously. Children reached out and touched a small dot that appeared in one of four positions (±5° and ±10). Reach kinematic measures were time-to-reach onset, total reach duration, peak velocity, acceleration duration, and deceleration duration. Saccade kinematic measures were saccade latency, gain (i.e. accuracy), peak velocity, temporal eye-hand coordination (i.e., time between saccade and reach initiation), and percentage of trials with corrective saccades. Results: Reach kinematics. Compared with controls, children with deprivation amblyopia had increased total reach duration (mean±SD=501±31 ms vs. 552±62 msec; p=0.002), increased deceleration duration (311±34 ms vs. 359±54 ms, p=0.002), and lower peak velocity (1.37±0.17 m/s vs. 1.24±19 m/s; p=0.043). Time-to-reach onset and acceleration duration did not differ between groups (ps≥0.24). Saccade kinematics: Children with deprivation amblyopia produced more corrective saccades than controls (60±22% vs. 43±16% of trials, p=0.034). Saccade onset latency, saccade gain, peak velocity, and temporal eye-hand coordination did not differ between groups (all ps ≥0.18). Conclusion: Longer deceleration duration is consistent with results from strabismic children, and increased frequency of corrective saccades during reaching is consistent with data from strabismic adults. Lower peak velocity, longer deceleration in the final approach, and more corrective saccades may indicate impaired use of visual feedback.