Changes in refraction and biometry in emmetropic and myopic children: The SCORM study

Abstract

Myopia is a major public health problem and the prevalence of myopia in Singaporean children is one of the highest worldwide. A better understanding of the refraction and ocular components developments during childhood will enable better public health interventions for the prevention of onset and progression of myopia in children and adolescents.

Yearly cycloplegic refraction and ocular biometry measures collected from the school-aged children enrolled in The Singapore Cohort study Of the Risk factors for Myopia (SCORM) throughout the children?s elementary education were analysed. The children were classified into one of five refractive error groups based on the spherical equivalent of the randomly selected eye, measured during their ages of 6 to 13 years old for: persistent hyperopia, emmetropising hyperopia, persistent emmetropia, newly developed myopia and persistent myopia.

The overall aim of this thesis is to evaluate the ocular biometry growth, refractive error pattern and their correlations with quality of life in Singapore school-aged children. The aims include: i) To examine the changes in ocular components in children with emmetropia and those with refractive errors, including hyperopia and myopia during their ages of 6 to 13 years old, ii) To assess the changes in refractive error and ocular components before and after the onset of myopia among children, iii) To illustrate and present the utility of fractional polynomial in modelling longitudinal data in myopia, and iv) To assess the impact of presenting visual impairment and refractive errors on health-related quality of life measures in children and adolescents of Singapore.

Our findings showed that the axial length and vitreous chamber elongated with time with younger children showing a more rapid elongation which slowed with age. Faster elongation of axial length and vitreous chamber over time were observed in children with myopia when compared to those with emmetropia. There was a U-shaped growth curve for lens thickness and inverted U-shaped curve for anterior chamber depth. Our findings of early lens thinning followed by thickening, suggest a two-phase growth in the lens.

The eyes were found to have more negative refractive error, to grow longer axially, and have deeper vitreous and anterior chamber appearing at 2 to 3 years before the myopia onset in Asian children. The differences in corneal radius of curvature and thickness of lens were minimal between children with newly developed myopia and emmetropia. The spherical equivalent and major ocular components could potentially be used to predict the development of high myopia in children.

Our findings also indicated that the health-related quality of life (HRQoL) of children and adolescents was not compromised by refractive errors. The HRQoL of those with myopia, hyperopia, astigmatism and presenting visual impairment was not significantly lower. Similar results were found for the HRQoL reported by their parent proxy. Notably, our findings suggested that healthy adolescents with presenting better-seeing eye visual impairment reported lower total, psychosocial, and school scores. The concordance in QoL measures between adolescents with presenting better-seeing eye visual impairment or refractive errors and their parent proxy were small.