Abstract
Purpose:
To investigate the natural time course of change in nearwork-induced transient myopia (NITM), and its association with the progression of refractive error, in Beijing urban students.
Methods:
386 students (ages 6-17 yrs) were enrolled in the baseline study (year 2010) of the Beijing Myopia Progression Study (BMPS). These students were invited for additional follow-up vision examinations in the years 2011, 2012, and 2013, which included cycloplegic autorefraction. Initial NITM and its decay were assessed objectively immediately after binocularly-viewing and performing a sustained near task (5D, 5 minutes), to elicit NITM incorporating a high cognitive demand with full distance refractive correction in place.
Results:
222 students (57.0%) with both NITM and cycloplegic refractive data were enrolled. The initial NITM (median, lower and upper quartile) increased significantly in myopic students [0.16 (0.07, 0.27), 0.22 (0.13, 0.30) and 0.20 (0.11, 0.29) D, p=0.01]. Its decay time increased significantly in both myopic students [80 (30, 180), 120 (50, 80) and 90 (40, 180) seconds, p=0.03], and emmetropic students [40 (20, 120), 110 (40, 170) and 120 (50, 180) seconds, p=0.03]. For the hyperopic students, after adjusting for the children's age, gender, cycloplegic refraction at baseline, and parental refraction, their initial NITM at baseline and in the first year of follow-up were significantly associated with their corresponding years of refractive change, respectively (β=-1.37, p=0.02, and β=-1.89, p=0.01). The decay time in hyperopes in the first year of follow-up was significantly associated with their corresponding years refractive change (β=-0.01, p=0.02).
Conclusions:
In this sample of children, initial NITM slightly increased among the myopes, and remained stable in hyperopes. NITM was associated with the progression of refractive error only among the hyperopic students.