Analysis of visual functioning in children with autism suggests impairment in visual convergence.
A brief review of: Elizabeth Milne, Helen Griffiths, David Buckley, Alison Scope (2009). Vision in Children and Adolescents with Autistic Spectrum Disorder: Evidence for Reduced Convergence Journal of Autism and Developmental Disorders DOI: 10.1007/s10803-009-0705-8
Although clinical observations, previous research, and parental reports suggest that children with autism have atypical visual perception and functioning, including for example, greater visual acuity, increased sensitivity to light, and increased strabismus, our understanding of the possible underlying mechanism that may explain such visual anomalies is limited.
In the present study, the authors examined the visual functioning of 51 children with autism (44 males, 8 to 18 years old) and 44 typically developing kids (13 males, 8 to 17 years old). The following aspects of vision were examined: Visual Acuity, Steroacuity, vergence, convergence, prism fusion range, near point convergence, strabismus, ocular motility, and optokinetic response.
The authors found that 11% of the typically developing children and 31% of the ASD had a documented visual impairment (myopia, astigmatism, etc). This difference was statistically significant. That is, children with ASD were significantly more likely than typically developing children to have these conditions. Children with autism also displayed significantly poorer visual acuity (but within normal limits), and lower convergence. Convergence refers to the process by which the eyes move towards each other to maintain focus on approaching or close-range objects.
The findings of reduced visual acuity in children with autism when compared to typically developing children contradict previous studies that have shown enhanced visual acuity in autism. This brings us to a major limitation of this study that was correctly noted by the authors. It seems that the study was advertised as a study of visual functioning in autism. Thus, parents who responded to the initial recruitment efforts may have been more likely to have kids with visual problems. This would explain the high levels of visual problems observed in the autism group as well as the lower rates of visual acuity. Yet, the authors of this study also found lower incidence of strabismus than what has been reported in the past.
The issue of convergence is intriguing. Convergence is one of the mechanisms that we use to estimate depth and distance. Limited convergence therefore would be associated with more limited depth perception. I find this intriguing because the neuropsychological profile of children with high functioning autism is often very similar to what is observed in kids with non-verbal learning disabilities (including relative weaknesses in motor-visual functioning). In addition, many parents with children with ASD report that their kids have trouble with sports and other physical activities. I thus wonder how much the reduced convergence observed in ASD may affect the motor-visual functioning in autism.
Clinically, I was also intrigued by the high rates of vision problems found among the ASD group. Although, as I mentioned, this may be due to a self-selection of the parents who agreed to participate, this is consistent with data suggesting that children with developmental disorders are more likely to have visual problems than typically developing children. In our practice we recommend a visual screening to all children regardless of age, and these results support the need for more comprehensive visual screening in children with autism.
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