Cylinder power progression associated with axial length in young children: a two-year follow-up study

Purpose To describe the association of refraction development and axial length (AL) in young children and provide new insights into the progression of cylinder power. Methods Children (2-3 grades) were enrolled from primary schools in Shanghai and followed up for two years. Cycloplegic refraction, AL, and corneal curvature radius were measured. Refraction parameters were compared among groups with different AL, AL1 (AL < 23.5 mm), AL2 (23.5 mm <= AL < 24.5 mm), and AL3 (AL >= 24.5 mm). Multiple regression analysis was used to explore risk factors of diopter of cylinder (DC) progression. Results In total, out of 6891 enrolled children, 5961 participants (7-11 yrs) were included in the final analysis. Over the two-year period, the cylinder power significantly changed, and those with longer AL had more rapid DC progression over the two years (AL1, -0.09 +/- 0.35 D; AL2, -0.15 +/- 0.39 D; AL3, -0.29 +/- 0.44 D) (P < 0.001). The change in DC was independently associated with AL at baseline (P < 0.001). The proportion of with-the-rule astigmatism increased from 91.3% to 92.1% in AL1 group, from 89.1% to 91.8% in AL2 group and from 87.1% to 92.0% in AL3 group. Conclusions Young children with long AL experienced rapid progression of cylinder power. Both the control of myopia progression and attention to the correction of astigmatism are necessary in the health management of children with long AL. The significantly increased AL in participants might contribute to both the extent and direction of astigmatism.