Shifts in tonic accommodation after near work are related to refractive errors in children.

A link between changes in tonic accommodation (TA) produced by sustained near work and the development of adult-onset myopia has been suggested in studies of young adults. Measures of TA before and after near work have been lacking in children of school age, which is the most susceptible period for the development and progression of juvenile-onset myopia. In the present study accommodation was measured in 87 children, aged 7 to 16 years, before and after 15 minutes of video game playing. All children were refracted before testing and wore optical correction during measures of accommodation with a Canon R1 autorefractor. Most children showed initial values of TA (far focus minus dark focus) between 0.0 and 1.0 D, with a mean of 0.68 D. Grouped by refractive status, the myopic children initially showed 0.30 D of TA, while the emmetropic children showed 0.75 D and the hyperopic children showed 0.94 D. After playing the video game, TA of the myopes increased by 1.15 D, compared to smaller increases for the emmetropes (0.68 D) and hyperopes (0.24 D). Comparable values have been obtained from young adults. These results indicate that the smallest initial values of TA and the largest inward shifts in TA are found during the period of acquisition and progression of myopia, regardless of age.