Bifocals in Down Syndrome Study (BiDS): design and baseline visual function.

PURPOSE: Among children and young people with Down syndrome (DS) there is a high prevalence of reduced accommodation. Prescribing bifocals for these patients has not become fully clinically accepted, although it would be anticipated to improve visual acuity (VA). The aim of this study is to investigate the impact of bifocal correction on VA, visual perceptual skills and early literacy development in children with DS who have reduced accommodation and who are provided with a bifocal correction. This paper describes the study design and the baseline optometric findings.

METHODS: We have chosen a longitudinal design with frequent measures of subtests of performance to control for progression with time. The main outcome measures are early literacy and visual perception skills. Secondary outcomes are VA and accommodative function. These are measured at baseline, the participant followed for 6 months when bifocals are prescribed if necessary, and the participants were followed for another 6 months with bifocals.

RESULTS: Fourteen participants with DS aged 8 to 19 years were enrolled. At baseline 79% required a change in their distance spectacle prescription. One hundred percent had reduced accommodation both before and after new single vision glasses were prescribed. None had an adverse reaction to 0.5 or 1% Cyclopentolate. All the subjects were able to perform either a distance or near crowded Patti-pics symbols test and 93% were able to perform both. There was a significant improvement of near VA with the new single vision spectacles (p = 0.015). The mean binocular distance VA was 0.362 +/- 0.17 logMAR whereas binocular near VA was 0.489 +/- 0.235.

CONCLUSION: This study confirms previous findings of a high prevalence of reduced accommodation and shows that near VA is reduced compared to distance VA. The present results indicate that all subjects might benefit from bifocals.