Abstract
Purpose: :
To compare ocular component growth curves among 5 refractive error (RE) groups in Asian children.
Methods: :
A school-based, longitudinal cohort study (Singapore Cohort study Of the Risk factors for Myopia) of children aged 6 to 9 years commenced in 1999 and were followed up yearly. Analyses were restricted to visit data collected between the ages of 6 to 12 years and children with at least three visits. Autorefraction was performed yearly using the Canon RK-F1 autorefractor after 3 drops of 1% cycloplentolate and biometry measures were taken using the A-scan ultrasound machine. The 5 RE groups were defined as follows: persistent hyperopia of spherical equivalent (SE) > +1.00D at all visits (n=49); emmetropizing hyperopia of SE > +1.00D on at least the first visit but being between -0.50D (exclusive) and +1.00D at subsequent visits (n=143); persistent emmetropia of SE between -0.50D (exclusive) and +1.00D at all visits (n=372); emmetropic children who became myopic of SE between -0.50D (exclusive) and +1.00D on at least the first visit and with ≤ -0.50D at one or more subsequent visits (n=615); persistent myopia of SE ≤ -0.50D at all visits (n=596). One eye was randomly selected from each child. The growth curves for axial length (AL), vitreous chamber depth (VCD), anterior chamber depth (ACD), lens thickness (LT) and corneal curvature (CC) of all children were modeled using mixed effect linear models and the curves of persistent emmetropes were compared to other groups.
Results: :
Of the 1979 children, 1775 (90%) were analysed. Persistent myopes and emmtropes who became myopes had faster lengthening of AL and deepening of the VCD (increased by 0.3mm per year, p<0.001) than persistent emmetropes. Faster growth in ACD (p=0.009) and thinning in lens (p<0.001) was also found in emmetropes who became myopes, but not in persistent myopes when compared to persistent emmetropes. However, the CC pattern of myopes was not different from persistent emmetropes. There were no significant differences in ocular components of growth between emmetropizing or persistent hyperopes, and persistent emmetropes. These results remain unchanged after adjusting for gender, ethnicity and father’s education level.
Conclusions: :
The ocular component growth curves of Asian myopic children were different from emmetropic children, whereas the hyperopes had similar growth to emmetropes.
Keywords: myopia • refractive error development • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology