Patterns in longitudinal growth of refraction in Southern Chinese children: cluster and principal component analysis

Abstract

In the present study we attempt to use hypothesis-independent analysis in investigating the patterns in refraction growth in Chinese children, and to explore the possible risk factors affecting the different components of progression, as defined by Principal Component Analysis (PCA). A total of 637 first-born twins in Guangzhou Twin Eye Study with 6-year annual visits (baseline age 7-15 years) were available in the analysis. Cluster 1 to 3 were classified after a partitioning clustering, representing stable, slow and fast progressing groups of refraction respectively. Baseline age and refraction, paternal refraction, maternal refraction and proportion of two myopic parents showed significant differences across the three groups. Three major components of progression were extracted using PCA: "Average refraction", "Acceleration" and the combination of "Myopia stabilization" and "Late onset of refraction progress". In regression models, younger children with more severe myopia were associated with larger "Acceleration". The risk factors of "Acceleration" included change of height and weight, near work, and parental myopia, while female gender, change of height and weight were associated with "Stabilization", and increased outdoor time was related to "Late onset of refraction progress". We therefore concluded that genetic and environmental risk factors have different impacts on patterns of refraction progression.

Figure 1. Partitioning clustering of longitudinal refraction in first-born twins.

Upper left: refraction change over age in right eyes of all subjects. Upper middle: three clusters of progressing pattern. Upper right: The medoids in the three clusters. Lower row shows that the distributions of cluster 1 to 3 with age respectively.

Figure 2. Component loadings plots of the first three principal components of longitudinal patterns in refraction.

Figure 3. The patterns of different principle component scores in refraction progression (PC: principle component; SE: spherical equivalent).