The higher prevalence of autism reported in blind children has been commonly attributed to the confounding effects of an underlying intellectual disability. The aim of this study was to explore the relationship between symptoms of autism and blindness in adults with intellectual disability. We hypothesized that blindness can increase the probability of the autism phenotype, independent of known risk factors, that is, severity of intellectual disability and gender. A general population case register (population size of 0.7 million) was used to conduct two studies. The first study was on 3,138 adults with intellectual disability, using a validated autism risk indicator to study adults with visual impairment. This identified 386 adults with partial and complete visual impairment, both of which were associated with presence of high number of autistic traits (P < 0.001). The second study was only on those with congenital blindness using a standardized assessment tool, the Pervasive Developmental Disorder-Mental Retardation Scale. Those with hearing impairment or unilateral, partial, and acquired visual impairment were excluded. Control groups were randomly selected from those with normal hearing and vision. Prevalence of the autism phenotype was higher among those with congenital blindness (n = 46/60; 76.7%) than their controls (n = 36/67; 53.7%) and this association was statistically significant (adjusted odds ratio = 3.03; 95% confidence interval: 1.34-6.89; P = 0.008). Our results support the hypothesis that a congenital blindness independently affects psychosocial development and increases the probability of the autism phenotype. Early identification of autism could facilitate appropriate psychosocial interventions and educational opportunities to improve quality of life of people with blindness. Autism Res 2019, 12: 1411-1422. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Although autism has been commonly reported in those with blindness, it is generally attributed to an accompanying intellectual disability. Current study, however, revealed that congenital blindness is independently associated with symptoms of autism. In spite of its high prevalence, autism can be overlooked in those with intellectual disability and blindness. Improving diagnosis in this population should, therefore, be advocated through raising awareness of this association to facilitate early access to services.
Keywords: autism spectrum disorder; congenital blindness; intellectual disability; learning disability; visual impairment.
© 2019 International Society for Autism Research, Wiley Periodicals, Inc.