Motor skills of children with unilateral visual impairment in the Infant Aphakia Treatment Study

Although unilateral visual impairment (UVI) is a common pediatric vision disorder, its functional significance is not fully understood1. Hyperopic refractive errors identified at infant screening are associated with poor visuomotor test performance in early childhood2, but it is unclear to what extent UVI affects children’s motor development. UVI and associated abnormalities of binocular depth perception result from a number of conditions, including eye misalignment (strabismus), refractive imbalance (anisometropia), or image deprivation (e.g., from cataract). Treatment of these conditions typically includes occlusion of the eye with better vision during a sensitive period for visual development, which coincides with the stage during which children develop and integrate key motor skills, including reaching/grasping and postural stability and control. Therefore, children with UVI may be at risk for delayed development of motor skills due to poor vision, lack of binocular function, and/or to lack of practice in ambulating or manipulating objects. Children with UVI resulting in amblyopia generally perform worse on tests of motor skills than age-matched children with normal vision, particularly on fine motor tasks that require speed and dexterity1, 3–5. However, only some of these studies used standardized, norm-referenced tests to assess motor skills, and none examined multiple domains of motor functioning. Most of this research assesses only fine motor skills or eye-hand coordination. Relatively few studies measured postural control/stability or gross motor skills of children with UVI. Arguably, UVI and associated deficits in binocular vision might interfere in performance of tasks assessing balance, posture, and gait, as these activities require integration of vestibular signals relating to head or body position/motion with proprioceptive information and visual perception of the environment. There are no published reports of motor skills in children with UVI secondary to unilateral congenital cataract. It is unclear to what extent the relatively poor motor test performance of children with UVI is due to poor visual acuity in the affected eye, to reduced binocular vision, or both. Multiple regression analyses suggest that strabismus5 or reduced stereovision4 has a greater adverse impact on fine motor performance than the degree to which the two eyes differ in acuity among children with amblyopia. However, the relative importance of stereopsis versus degree of amblyopia may vary according to the child’s age3, given developmental changes in reach-to-grasp strategies6. The Movement Assessment Battery for Children – 2nd edition (MABC-27), a standardized, norm-referenced assessment of children’s everyday motor competence, includes eight tasks assessing three domains: manual dexterity, ball skills, and static and dynamic balance. The primary aim of this study was to assess motor functioning using the MABC-2 in 4.5 year old children enrolled in the Infant Aphakia Treatment Study (IATS), a randomized, multicenter (n = 12) trial comparing treatment with a primary intraocular lens (IOL) or contact lens (CL) in 114 infants with surgery for unilateral cataract extraction between 1 and 7 months of age. Key research questions include the following: (a) Are there significant differences in motor functioning between the treatment groups? (b) How does the motor functioning of the IATS sample compare to that of the MABC-2 standardization sample? (c) To what extent are motor skills predicted by visual acuity and/or stereopsis? Multivariate analyses control for earlier age of surgery and the absence of strabismus, as these variables have been associated with better stereoacuity in previous studies (8, 9).