Bifocals and Down's syndrome: correction or treatment?

PURPOSE: Accommodation is reduced in approximately 75% of children with Down's syndrome (DS). Bifocals have been shown to be beneficial and they are currently prescribed regularly. Clinical observations suggest the likelihood of improving accommodative ability after bifocal wear. The aim of the study is to evaluate the potential use of bifocals as a treatment for the reduced accommodation. METHODS: Clinical records of 40 children from the Cardiff Down's Syndrome Vision Research Unit, who were prescribed bifocals, were reviewed. Accommodation was noted before wearing the bifocals and during either their latest visit or when the children stopped using bifocals. Accommodation was reassessed during a follow up visit for the children who stopped wearing bifocals. Development of accommodation before bifocal commencement, age at bifocal prescription, gender, type of refractive error, visual acuity and the presence of strabismus were examined to evaluate their contribution to accommodation improvement. RESULTS: The accommodative ability of 65% (n = 26) of the children improved (through the distance part of the lens) after using the bifocals. More than half of those developed accurate accommodation without the use of bifocals (n = 14). Accommodative responses did not show any improvement with age before the children began wearing bifocals. Accurate accommodation was sustained after returning to single vision lenses in all examined children. The age distribution of the children on bifocal commencement was diverse. Presence of strabismus, refractive error type, visual acuity and gender did not have any effect on gaining improvement. CONCLUSIONS: Bifocals are an effective correction for the reduced accommodation in children with DS and also act to improve accommodation with a success rate of 65%. Bifocal wear can therefore be temporary, i.e. a 'treatment' for the deficit, in at least one third of children.

Development and distribution of refractive error in children with Down's syndrome.

AIM: Previous studies have described the emmetropisation process as inactive in Down's syndrome (DS). However, these studies investigated only a small age range of children-either young children or teenagers. The present study aims to describe refractive error development and distribution in DS throughout childhood and early teenage years. METHODS: Subjects were recruited from the Cardiff University Down's Syndrome Vision Research cohort. Refractive error was measured using Mohindra retinoscopy. Subjects were grouped into 15 yearly age groups to allow a cross-sectional assessment of refractive error distribution (n=182). Longitudinal refractive development was observed in 12 children with DS whose refractive error had been monitored throughout their childhood and teenage years. RESULTS: Children were hypermetropic, on average, at all ages, albeit with a wide variation in refractive errors. Change in power vector components, M, J(0) and J(45), and the presence of significant astigmatism (≥1.00 D) was assessed with age. There were no statistically significant difference in M and J(0) across age groups. However, there was a significant difference in J(45). Prevalence of significant oblique astigmatism increased with age and was highly prevalent (45%) in teenage years. Longitudinally, no significant change in refractive error was reported with regards to the spherical component. CONCLUSION: The results provide further evidence of the failure in the emmetropisation process in children with DS. Change in spherical refractive error is minimal throughout childhood and early adulthood. The children show a specific development of oblique astigmatism that may be suggestive of a mechanical induction through eyelids.