Eye-hand coordination during visually-guided reaching in children with monocular deprivation amblyopia

Monocular deprivation (MD) amblyopia caused by a dense unilateral congenital or infantile cataract leads to both sensory and ocular motor deficits, which can in turn affect motor performance. Previous research shows reduced fine motor skills in children with MD amblyopia on standardized tasks. Here, we evaluate eye-hand coordination during visually-guided reaching in MD amblyopia. A group of 17 children aged 7-15 years with MD amblyopia resulting from a unilateral cataract and a group of 41 age-similar control children were enrolled. During binocular viewing, children's reaching movements (LEAP Motion Controller) and eye movements (EyeLink 1000 binocular eye tracker) were recorded as they reached to touch a dot displayed at one of four locations (±5 deg or ±10 deg) on a computer monitor. Saccade and reach kinematic measures were assessed between groups, and factors associated with impairments in the MD amblyopia group were evaluated. The MD amblyopia group as a whole had impaired saccade (lower saccade gain, reduced saccade precision, more reach-related saccades) and reach (longer total reach duration, slower peak velocity, reduced touch accuracy) kinematics compared to controls. However, performance was worse in those with a poorer visual acuity outcome (≥0.7 logMAR) compared to good visual acuity outcome (≤0.6 logMAR). MD amblyopia impacts the development of eye-hand coordination during reaching, particularly in those with a poorer visual acuity outcome. Longer deceleration in the final approach and more reach-related saccades may suggest an inability to adapt or form an efficient compensatory strategy and may also be indicative of impaired on-line control.