Bifocals reduce strabismus in children with Down syndrome: Evidence from a randomized controlled trial.

PURPOSE: Children with Down syndrome (DS) more often have strabismus, refractive errors, accommodative lags and reduced visual acuity (VA) than typically developing children. In this study, we compare the effects of bifocal glasses with those of unifocal glasses in children with DS. Changes in angle of strabismus, accommodation and refractive error were analysed in this paper. METHODS: In a multicentre randomized controlled trial, 119 children with DS, aged 2-16, were randomly allocated for bifocal or unifocal glasses (with full correction of refractive error in cycloplegia). The 15 centres, all in the Netherlands, followed the participants for 1 year. Changes in refractive error, accommodative accuracy, strabismus, binocularity and stereopsis were compared across 4 subsequent visits. RESULTS: Refractive errors and accommodative errors showed no significant change throughout the course of our study in either intervention group. The manifest angle of strabismus, however, reduced significantly in the bifocal group. This improvement was observed shortly after the children received their new correction (~6 weeks) (linear regression: t = 3.652, p < 0.001) and remained present in the final measurements after 1 year (linear regression: t = 3.604, p < 0.001). The percentage of children with positive binocularity and stereo tests showed no significant differences between the groups. CONCLUSION: Bifocals with full correction of refractive error reduce the manifest angle of strabismus within a few weeks. No effects on accommodation, refractive error, stereopsis and binocularity occurred over the course of 1 year.

Young children's use of a visual aid: an experimental study of the effectiveness of training.

We report an experiment concerning the use of a stand magnifier by young children with visual impairments (21 males, 12 females; mean age 4y 8mo [SD 11mo]). Children had a normative developmental level and a visual acuity of 0.4 or less (< or =20/50 in Snellen's notation). To measure magnifier use objectively, we developed a task that closely resembled the dynamics of its real-life (pre-reading) use. Children had to follow trails visually, from a start location to an unseen end location. This could only be done successfully and reliably by proper use of the magnifier. In addition to this, we analyzed the effect of specific training with the magnifier by using a repeated-measures (before and after training) matched-groups (with respect to age and near-visual acuity) design. Results established both the task's efficacy as an instrument for measuring magnifier use in young children and the effectiveness of the training. Improvement in task performance after training was found in both groups, except for the youngest children (<3y 6mo). On average, 1.8 times as many paths were followed in both groups after training (p=0.001). The without-magnifier training group became 2.5 times as good at finding the correct end location, whereas the with-magnifier training group became 4.3 times as good (p=0.05).

Effects of bifocals on visual acuity in children with Down syndrome: a randomized controlled trial.

PURPOSE: Children with Down syndrome (DS) typically have reduced visual acuity (VA) and accommodation lag, but it is unclear whether prescribed glasses should correct both distance VA (DVA) and near VA (NVA) due to the lack of RCTs. We therefore conducted a multicentre RCT to compare the effects of bifocals designed to correct both DVA and NVA with distance-correcting unifocal glasses in children with DS. METHODS: A total of 119 children with DS, aged 2-16, were randomly allocated for bifocal or unifocal glasses (with full correction of refraction error in cycloplegia) in 14 Dutch hospitals and followed during 1 year. VA data were analysed in relation to baseline VA with ancova. RESULTS: Treatment groups showed no differences at baseline. Shortly after receiving new corrections (~6 weeks), uncrowded NVA (bifocals 0.18 ± 0.33 LogMar; unifocals 0.09 ± 0.19 LogMar) and crowded NVA with bifocals (bifocals 0.13 ± 0.36 LogMar; unifocals 0.08 ± 0.33 LogMar) were significantly better than at baseline, but these short-term improvements in NVA were not significantly different between the two treatments (p > 0.151). The 1-year treatment differences were as follows: significantly larger improvement for bifocals compared to unifocals in both uncrowded NVA (bifocals 0.23 ± 0.29 LogMar, unifocals 0.12 ± 0.30 LogMar, p = 0.045) and crowded NVA (bifocals 0.31 ± 0.28 LogMar; unifocals 0.16 ± 0.30 LogMar, p = 0.017). Improvements in DVA were comparable (bifocals 0.07 ± 0.21 LogMar, unifocals 0.08 ± 0.22 LogMar, p = 0.565). Children with poor baseline VA improved more. Accommodation lag stayed unchanged. CONCLUSION: After one year, bifocals with full correction of ametropia led to significantly larger improvement of both uncrowded NVA and crowded NVA in children with DS with accommodation lag compared to unifocals.

Effect of visual impairment on goal-directed aiming movements in children.

This study investigated potential differences in motor control between children with a visual impairment (diagnosed albinism; n=11, mean age 8y 4mo [SD 7mo]; seven males, four females,) and children with normal vision (n=11, mean age 8y 4mo [SD 7mo]; six males, five females). Mean near visual acuity in the albinism group was 0.19 (SD 0.07, Snellen: 20/104). Children performed two types of movements (discrete and cyclic) in two orientations (azimuthal and radial, i.e. along the viewing and lateral direction), and with two amplitudes (10 and 20cm). All movements were performed in two subsequent target conditions: with and without visual information on the target location. Overall, children with visual impairment displayed larger endpoint variability. Discrete movements and movements over large distances were less fluent in both groups, but especially in the children with visual impairment. Children with visual impairment seemed to have more difficulties with calibrating the sensory information. Specifically, they made larger errors along the lateral direction, when the target was not visible. Results suggest that children with visual impairment have specific differences in motor control compared with children with normal vision, which are not all directly related to their poorer vision.

Changes in causes of low vision between 1988 and 2009 in a Dutch population of children.

PURPOSE: Causes of low vision in the Netherlands may have changed over time. The purpose of this study is to assess trends over the last two decades. METHODS: Socio-demographic and medical data, including ophthalmic diagnosis and inheritance patterns for 2843 children with low vision (0-21 years; 50% representation) referred to a Dutch institute for low vision (Bartiméus) over a 21-year period between 1988 and 2009, were included in the analysis. For the 19 most common diagnoses, inheritance and presence of mental impairment, trend analyses were performed with logistic regression models; odds ratios (OR) for a 10-year time span were reported. RESULTS: Cerebral visual impairment (CVI) was found in 27.2% (97% mental impairment), albinism in 8.0%. Over time, nystagmus (6.6%; OR = 1.42), retinitis pigmentosa (2.9%; OR = 1.61), cone-rod dystrophy (2.6%; OR = 1.98) and hyperopia (2.0%; OR = 3.66) increased significantly. Cataract (4.9%; OR = 0.64), aniridia (1.6%; OR = 0.42) and retinopathy of prematurity (ROP; 2.0%; OR = 0.45) decreased significantly. There was a significant increase in genetic disorders (41.0%; OR = 1.49) and in co-occurrence of mental impairment (52.2% OR = 1.16). CONCLUSION: In the last two decades, treatable or preventable disorders (such as cataract and ROP) have become a less common cause of low vision in children. However, the prevalence of complex (genetic) and untreatable disorders (CVI) has taken its place, as a result of increased survival of preterm and low birth weight children and improved diagnostic possibilities. Knowledge of the prevalence of low vision, its causes and trends over time may help policy makers to define effective intervention strategies and to monitor its impact.