For children, deficits of one particular sensorimotor function, visuomotor, have been, according to Aylward (2002), very hard to identify and, consequently, to study and estimate their prevalence. One of reasons is that they have been described using several terms e.g as visual-motor control, visual-perception, visuomotor integration, and eye-hand coordination. In this thesis, both studies relating to visual processing (perception) and, the ones that relate to visuomotor skills, are presented in the same section as the terms often overlap in literature, and a differentiation is beyond the scope of this thesis.
In a population-based, GA criterion referenced study by Cooke et al (2004), an ophthalmologic examination was performed on 279 preterm 7-year old children (GA<32 weeks) who attended mainstream schools, and did not present with a severe neurodevelopmental sequelae. The findings revealed a significantly higher prevalence of visual problems than those of their term controls, matched for sex, first language, and birth date. The preterm children were more likely to wear glasses (p=.002), had a poorer visual acuity (p=007, left eye; p=002, right eye) and, reduced stereoscopic vision (p<.001. Moreover these ophthalmologic problems significantly related to results from tests that examined the children’s motor skills (ABC) (Henderson & Sugden, 1992), cognitive skills (WISC-III) (Wechsler, 1991 cited by Cooke et al, 2004) and, visuomotor integration (VMI) (Beery & Buktenika, 1989 cited by Cooke et al, 2004), with the strongest association revealed being the one between visual impairments and motor impairment (p<.001). Moderate level of retinopathy of prematurity, an ophthalmologic condition particularly related to preterm birth in which
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an abnormal growth of blood vessels can lead to bleeding, formation of scars, and consequent damage of the retina of the eye, was found to correlate to wearing glasses (p=.01). Family histories, of the children that participated in the study, were however not factored into the analysis of the data. Therefore a potential link between family history and visual problems could not be controlled for.
Similarly in the prospective follow-up study of Luoma, Herrgård and Martikainen (1998), 46 children born prematurely (<32 weeks) were compared at the age of five on several neuropsychological functions, with a control group matched for age, sex, and parental occupational/ educational status. The neuropsychological assessment focused on the sensorimotor and visuoperceptual functions. A variety of valid and reliable tests were used such as Wechsler Preschool and Primary Scale of Intelligence (WPPSI), the Neuropsychological Investigation for Children (NEPSY), and the Visuomotor Integration test (VMI). In almost all neuropsychological tests, there was a difference in favour of the control group, with the most significant difference being in the visuomotor performance (p=0.00). More specifically preterm children appeared to have problems with tactile and kinaesthetic awareness as well as with the voluntary movement of their arms, potentially, explaining problems with drawing, perceiving direction and space etc. Visuospatial deficits coexisted with visuomotor ones but to a lesser extent (see visual problems). These findings appear to agree with those of Cooke et al (2004). According to Luoma, Herrgård and Martikainen (1998), visuomotor and visuospatial functions are closely associated with writing/reading and arithmetic performance at school age respectively.
Jongmans et al (1996a) investigated the relationship between visual abnormality and perceptual-motor problems in a cohort of 141, 6-year-old premature (GA<34 weeks) children who attended mainstream schooling in Hammersmith, UK. The children participated in a prospective follow-up study and were all graduates of a Neonatal Intensive Care Unit (NICU). The findings showed that the preterm children were significantly different (lower scores; p<0.05) in their visual abilities- both linear acuity and weak stereoscopic vision compared to the reference group, matched for age, gender and ethnic origin. The majority were children with a mild impairment. Also
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significant was the association between stereoscopic vision and perceptual-motor ability as measured by the M-ABC and the VMI (p<0.01 and p<0.05 respectively).
These findings highlight the importance of early ophthalmologic and visual function examination in order to gain awareness of delays in other functional domains. The findings of the study appear to agree with those of Cooke et al (2004) who have also reported visual acuity and stereoscopic vision deficits interfering with motor performance and visual-motor integration. One of the limitations of Jongman et al' s (1996a) study, was that ophthalmologic assessment was not performed in all cases.
This means that the increased prevalence of visual dysfunction in the preterm group can only be partly attributed to ophthalmologic problems. Moreover, the participants were all drawn from one particular hospital, with no information provided by the authors as to whether the selection of this setting was based on random sampling, or convenience.
Hård et al (2000) reported similar findings to the above studies when exploring the vision of 51 preterm children (GA<29 weeks). The preterm group was found to present with some kind of visual abnormality such as reduced visual acuity, strabismus or impaired stereoscopic vision when compared to their, matched for age, full-term controls at the age of 7 (median age=7.2 years). Ophthalmologic problems appeared in 61% of the cases, with 6% of those being visually impaired. The incidence of visual problems appears higher when compared to the findings of Cooke et al (2004) but the sample of this study also included children who had a different degree of prematurity (GA< 29 weeks), as well as children with known brain lesions and conditions such as cerebral palsy, as opposed to the study of Cooke et al (2004) where the participants did not present with a severe neurodevelopmental problems.
Visual perception, the ability to interpret, remember and understand what has been seen (Hård et al, 2000), was impaired in 42% of all preterm children and 34% of the cases (when those with brain lesions were excluded).
Finally, in the study of Stjernqvist and Sverringsen (1999), in Sweden, one of the few long-term, population-based studies that have used GA as a reference criterion for prematurity (GA<29 weeks), the general health, cognitive and general educational
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outcome of 61 extremely preterm children was compared to the one of their 61 full-term (FT) peers. The need for visual aids such as spectacles, was found to be greater (p<0.001) for the preterm group when compared for several neurodevelopmental outcomes with their full-term peers at the age of 10 years.