Myopic children show greater accommodative variability than emmetropic children

Children with early-onset myopia appear to demonstrate greater accommodative variability than emmetropic children and may show similar response patterns to patients with adult late-onset myopia, according to a study by researchers in Norway and the United Kingdom. This elevated variability could increase retinal blur for both near and far targets, the authors noted.

"Prospective longitudinal studies with larger sample sizes will be needed to isolate cause and effect for this potential stimulus to myopia," the authors said.

To identify the lag and variability of accommodation in children with early-onset myopia Trine Langaas, PhD, and colleagues obtained accommodation and pupil size measurements for 21 children who had a mean 1.26 D of myopia and averaged 14.14 years and 18 emmetropic children who averaged 13.51 years. The researchers used a PowerRefractor II (PlusOptix) instrument to obtain all measurements while children viewed targets set at three accommodative demands: 0.25 D, 2 D, and 4 D.

The researchers reported no difference in accommodative lag between groups. However, when viewing both the near (4 D) and far (0.25 D) targets, the accommodative response was more variable in myopes than in emmetropes, according to the study.

Additionally, there was a significantly larger mean lag of accommodation for both groups when viewing the 2 D target.

Variation in pupil size and variability were not sufficient to explain differences in accommodation variability among both groups, the authors noted.

"Since children with early-onset myopia show a similar pattern of change in the variability of the accommodative response with the target distance to that found in adults with late-onset myopia, [this study] provides evidence supporting a role for increased variability of accommodation in the etiology of both early- and late-onset myopia," they said.

The study is published in the January issue of Optometry and Vision Science.