Motor skill performance of school-age children with visual impairments S Houwen* MSc; C Visscher PhD; K A P M Lemmink PhD; E Hartman PhD, Center for Human Movement Sciences, University Medical Center Groningen, University of Groningen, the Netherlands. *Correspondence to first author at Center for Human Movement Sciences, University Medical Center Groningen, Section F, PO Box 196, 9700 AD Groningen, the Netherlands. E-mail:
[email protected] DOI: 10.1111/j.1469-8749.2007.02016.x
The aim of this study was to examine the performance of children with visual impairments (VI) aged 7 to 10 years on different types of motor skills. Furthermore, the association between the degree of the VI and motor performance was examined. The motor performance of 48 children with VI (32 males, 16 females; mean age 8y 10mo [SD 1y 1mo]) was assessed using the Movement Assessment Battery for Children (MABC). Their performance was compared with 48 children without VI (33 males, 15 females; mean age 8y 9mo [SD 1y 1mo]). Children with VI showed the poorest performance compared with peers without VI on unimanual speed, eye-hand coordination, catching, static balance, and dynamic balance while moving slowly. There was no significant difference between children with moderate and severe VI, except for bimanual coordination in 7- to 8-yearolds and eye-hand coordination in both the 7- to 8-year-olds and 9- to 10-year-olds, favouring the children with moderate VI. The poor performance compared with children without VI is related to vision, but the degree of the VI does not appear to relate to motor performance, except when associated with bimanual and eye-hand coordination. For children with VI, it seems very important to adjust the environmental context and task to enhance motor performance.
Motor skill performance can be seen as the interaction between a child’s characteristics and capabilities with environmental and task characteristics.1–3 For children with visual impairments (VI; best corrected visual acuity ≤ 6/18 [0.3] in the better eye),4 their visual impairment may act as a constraint, slowing down motor skill acquisition or leading to qualitatively different motor skills.5,6 Earlier studies have shown that children with VI generally have lower motor performance than their peers without VI, but also that some motor tasks are a more difficult than others.7–9 However, as previous studies have either focused on a subset of motor skills8,9 (e.g. manual dexterity) or have compared motor skill areas7 (e.g. gross motor skills vs fine motor skills) without focusing on specific motor skills, the question remains whether all motor skills cause difficulty for children with VI or only more visually demanding motor skills. That some motor tasks lead to more problems for children with VI may be related to the extent to which visual information is necessary for successful performance.10 This depends on the environmental context and type of task. Children with VI may be more adversely affected in environments with changing conditions, as visual information is important for updating representations of body, motion, location, and orientation.10,11 Similarly, the demands of the task may increase or decrease the need for visual information for successful performance.12 If children cannot accurately use visual information, intuitively one might expect the greater the VI the worse the motor performance. The association between the degree of VI and motor performance is, however, not clear.13 Although studies showed primarily that some residual vision is facilitative for motor performance,7,14,15 there are also examples where children with more residual vision do not necessarily perform better than children with little or no vision.8 Furthermore, the majority of previous research on the effect of the degree of VI has primarily focused on blind children versus children with residual vision,9,16 making it difficult to conclude in which way different degrees of VI are associated with motor performance. Therefore, the purpose of the present study was to investigate the motor performance of children VI with respect to manual dexterity, ball skills, and balance. From the literature, it has been established that children with VI perform worse than children without VI on these skills.7–9 Although a disadvantage for children with VI can be expected, it would be interesting to know whether the disadvantage is the same for different types of motor skills. We believe that although children with VI generally have an overall impairment compared with peers without VI, their motor problems vary both in nature and severity. Furthermore, this study also aimed to determine whether there was an association between the degree of VI and motor performance. Method PARTICIPANTS
See end of paper for list of abbreviations.
Children with VI aged 7 to 10 years were recruited from two Dutch educational institutes for children with VI (Sensis, in the city of Grave, and Visio, in the city of Haren). Only children who attended age-appropriate classes at mainstream schools were selected for the present study, which implies cognitive and social development in the normal range. Children with other non-visual-related impairments, such as
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neurological, physical, or medical conditions that may interfere with the aims of the present study, were excluded. Families of children who fulfilled these criteria were contacted by letter. Informed consent to participate was obtained from the children’s parents. The procedures were in accordance with the ethical standards of the Faculty of Medical Sciences of the University Medical Center Groningen, University of Groningen. MOVEMENT ASSESSMENT BATTERY FOR CHILDREN
The Movement Assessment Battery for Children (MABC) is a test battery designed for assessment of the everyday motor competence of children aged 4 to 12 years.17 There are four age-related item sets, each consisting of eight items; three items measure manual dexterity, two measure ball skills, and three measure static and dynamic balance. The items are scored 0 to 5, 0 being the optimal score. In the present study, only age bands 2 and 3 were used according to the ages of the children. The test has acceptable validity and reliability.17,18 Interrater reliability ranges from 0.70 to 0.89 and the test–retest reliability is 0.75.17 A pilot study with 15 children (10 males, five females) with VI aged 6 to 12 years, who were not involved in the present study, was conducted to examine test–retest reliability. Five children had severe VI (SVI) and 10 had moderate VI (MVI). It appeared that the test–retest reliability of the MABC over a 2-week interval was good (intraclass correlation coefficient>0.80). In the present study, the test was slightly adapted in order to enable the children with VI to perform the test. These adaptations included the use of materials with bright colours and increasing the visual contrast of materials. Furthermore, a child was allowed to feel the test materials before the test was administered. The modified materials were presented to both the children with VI and children without VI. These adaptations did not involve changes likely to influence the actual motor skills required when completing the task.
and 9- to 10-year-old children. The significance level was set at 0.05 for all analyses without correction for multiple comparisons, because a more stringent criterion would reduce the power, which increases the probability of type II error. To assist in determining the meaningfulness of group effects, correlational effect size statistics for the non-parametric data and accompanying 95% confidence intervals (CI) were calculated for each dependent variable according to Rosenthal and Rubin.19 An effect size of r=0.10 was defined as small, r=0.30 as medium, and r=0.50 as large.20 A linear function of medians with 95% CI was used to compare motor performance in younger and older children with VI and children without VI as an alternative to the parametric two-way analysis of variance (ANOVA).21 Children with SVI and MVI were taken as one group in the analyses when there was no difference in performance between these two groups. For bimanual and eye-hand coordination, the analyses were done separately for children with SVI and MVI. If 0 lay within the 95% CI of the median difference, we concluded that no significant difference existed in medians between the 9- to 10-year-old children with VI and their peers without VI compared with the 7- to 8-year-old children with VI and their peers without VI. Results RECRUITMENT
A total of 71 children aged 7 to 10 years with congenital bilateral VI were identified as being potentially eligible to participate in the study. Families of these 71 children were contacted by letter, and 48 (68%) of them agreed to participate. The participating and non-participating children were compared for demographic details of age, sex, and degree of VI. No significant difference was found between participants and non-participants for age (p=0.454), sex (p=–0.632), and degree of VI (p=0.454). CHARACTERISTICS OF PARTICIPANTS
STATISTICAL ANALYSIS
The statistical analysis were performed using SPSS software (version 12.0). For evaluating the differences between children with SVI, children with MVI, and children without VI, the non-parametric Mann-Whitney U test was used. Analyses were conducted separately for the two age groups because the MABC has two different formats for 7- to 8-year-old children
Table I: Anatomical causes of visual impairments of the children (n=48) Cause
7- to 8-year-olds (n=25)
Whole globe and anterior segment Glaucoma Uvea Retina Optic nerve Nystagmus Other Unknown
0 0 1 13 0 10 6 0
9- to 10-year-olds (n=23) 1 2 1 12 1 14 2 1
Values are number of children. Total exceeds 100% as some children had several sites affected.
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Children with VI The sample consisted of 25 children with VI (14 males, 11 females) aged 7 to 8 years (mean age 8y [SD 6mo]) and 23 children with VI (18 males, 5 females) aged 9 to 10 years (mean age 9y 9mo [SD 7mo]). Data on the VI were extracted from medical records. Table I shows the anatomical causes of the VI of the children. According to the definition of the World Health Organization,4 the children were classified as having low vision. For the children aged 7 to 8 years, nine children had SVI, i.e. acuity of less than 20/200 (0.10 with correction; better eye provides vision from a distance of 20ft that is equal to what a child without VI can see at 200ft; mean visual acuity in the present study: 0.09 [SD 0.03], range 0.05–0.10), and 16 children had MVI, i.e. acuity of less than 20/60 (0.30) but more than 20/200 with correction (mean visual acuity in the present study: 0.26 [SD 0.06], range 0.13– 0.30). There was no apparent visual field restriction in 23 children. One child had slight central visual field restriction and one child had slight peripheral visual field restriction. For the children aged 9 to 10 years, 10 children had SVI (mean visual acuity in the present study: 0.10 [SD 0.02], range 0.05–0.10) and 13 children had MVI (mean visual acuity in the present study: 0.27 [SD 0.05], range 0.13–0.30). There was no
apparent visual field restriction in 20 children. Three children had a slight central visual field restriction. Comparisons Twenty-five children without VI (16 males, nine females) aged 7 to 8 years (mean age 7y 11mo [SD 7mo]) and 23 children without VI (17 males, six females) aged 9 to 10 years (mean age 9y 8mo [SD 9mo]) from mainstream schools participated. They were selected from the classmates of the children with VI. The vision of the comparison children was checked based on teacher and parent reports. They indicated whether or not a child had visual problems. It appeared that no visual problem was present in the comparison children. MOTOR PERFORMANCE IN 7- TO 8-YEAR- OLDS
Table II shows the MABC scores of the children with SVI, children with MVI, and children without VI aged 7 to 8 years. Table III shows that the scores of the children with SVI were significantly higher (i.e. worse performance) than those of the children without VI for unimanual speed (p=0.006,
r=0.46); bimanual coordination (p=0.002, r=0.50); eyehand coordination (p
