The effect of bifocals in children with Down Syndrome

Near vision, is reduced in 86 to 100% of the children with Down Syndrome (DS)
34,45,49. This is an additional barrier achieving their maximum potential in
development.45
DS is one of the most common genetic anomalies, occurring in about 14.6 in
10000 live births in the Netherlands in 2007. In the last two decades many
research is done to find out the differences in ocular findings between
children with and children without DS34,49. Refraction errors, which have to be
corrected with glasses, are common14,15,17,34,45,49 (percentages vary from 40
to 90%14) and aggravate over time. The accommodation (focussing for near) is
consistent reduced in 50 to 100% of children with DS15,17,18,19,29,45,46,49 and
does not improve with age19
In contrast to children without DS glasses for distance vision don*t improve
near vision.17 Children with DS see blurred at near. Some authors have
suggested a relationship between this blurred retinal image and the absence of
emmetropisation (decrease of refraction error)15,17, others see a crucial
relationship with the defective visual development of children with DS,
presenting in visual acuities that do not reach normal levels17, generally
20/40 or lower49. Moreover the effort to accommodate may give rise to
strabismus, which occurs far more often in children with DS, in 15 to 47%14,34,
49 (versus 3 to 4% in normal population) and could be avoided or cured by
wearing the right glasses. Bifocal correction is such a tailor-made treatment
for the eye disorders in DS. Results shown in smaller studies on the effect of
bifocals are encouraging:
• Improved visual acuity for near19,29,46
• Significantly more accurate accommodation in the bifocal-treatment group19,29
• Positive impact on visual functioning: Faster and improved performance on
visual perceptual and some early literacy skills.45,46
• Bifocals were used with good compliance19,29,45,46
• Prevention of avoidable visual impairment

To prevent avoidable visual impairment, in our controlled study, we want to
contribute to the evidence of good treatment effects on visual functions
(visual acuity both distances near and at distance, accuracy of accommodation),
prevention of strabismus and development of task readiness using bifocal
correction in children with Down Syndrome.

A multicentre randomised controlled trail (RCT), the most suitable design for
effects of interventions.

Children in the intervention group will be prescribed adjusted bifocals and the
control group will be corrected in the usual way single vision glasses for
distance. Follow-up 1.5 years in 5 site visits.

Patient burden will not exceed the cooperation that is needed for normal visual
acuity controls and spectacle wear, except for the extra test for near vision,
measurement of accommodation and assessment of task readiness. Child-friendly
tests will be applied also for testing task readiness. These are like games.