Methods: A list of 121 items was generated from 13 focus groups with 4 children and young people with and without a visual impairment. A long 89 5 item questionnaire was piloted with 45 visually impaired children and young 6 people using face to face interviews. Rasch analysis was used to analyze the 7 response category function and to facilitate item removal ensuring a valid 8 unidimensional scale. The validity and reliability of the short questionnaire 9were assessed on a group of 109 visually impaired children (58.7% boys; 10 median age, 13 years) using Rasch analysis and intraclass correlation 11 coefficient (ICC).

The retention or development of infantile refractive errors in many children with Down syndrome indicates a failure of emmetropization. All children were at risk of strabismus whatever the refractive error. The findings have implications for timing of screening programs.

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Accommodation and visual acuity were measured in 53 children with Down's syndrome aged between 12 weeks and 57 months. Results were compared with data for 136 control (typically developing) children aged between 4 weeks and 48 months. Whereas the control children accommodated accurately on near targets, accommodation was defective in 92% of the children with Down's syndrome, and there was no change in accommodative ability with age. On the other hand, visual acuity lay within normal limits for the younger children. Children over the age of 2 years showed a below-normal visual acuity, which is not explained either by refractive error or by the effect of poor accommodation. The data suggest a sudden change in the rate of development of visual acuity which may be associated with physiological changes in the visual cortex. Previously reported defects of accommodation and visual acuity in older children and adults with Down's syndrome are confirmed by our findings in infants and young children.

The reduced visual acuity and contrast sensitivity in the Down syndrome group support the idea of an underlying sensory deficit in the visual system in Down syndrome.