Sex Differences in Rate of Axial Elongation and Ocular Biometrics in Elementary School Students

Abstract

Purpose

To determine the relationship between the ocular biometrics and axial length (AL) elongation and its rate in elementary school children.

Methods

This is a prospective observational study of 102 right eyes of third-grade elementary school students who were 8 to 9 years old. All participants underwent measurements of the AL, anterior chamber depth (ACD), and lens thickness (LT) annually for 3 years. The AL elongation during the first half and second half was calculated by subtracting the AL of the 1st year from that at the 2nd year, and AL of the 3rd year minus 2nd year. The total AL elongation (TALE) was obtained by summing up the first and second half AL elongations. The growth rate change (GRC) was obtained by subtracting the first half AL elongation from second half AL elongation. Spearman correlations were used to determine the correlation between the 1st year ocular biometrics and the TALE and GRC.

Results

The mean TALE was 0.54 ± 0.26 mm in boys and 0.46 ± 0.31 mm in girls. The mean GRC was 0.00 ± 0.16 mm in boys and −0.04 ± 0.14 mm in girls. In boys and girls, the TALE was significantly larger in the eyes with myopic ocular biometrics such as a deeper ACD, thinner LT, and longer AL during the 1st year (|r|=0.41 to 0.46, P < 0.05). The GRC was significantly accelerated in the eyes of only the girls with hyperopic ocular biometrics such as a shallower ACD, thicker LT, and shorter AL during the 1st year (|r|=0.31 to 0.41, P<0.05).

Conclusion

In boys and girls, the TALE tends to be larger in eyes with myopic biometrics at the 1st year examination. The GRC tended to accelerate in the eyes with hyperopic ocular biometry during the 1st year only in girls.

Keywords:

• axial elongation rate
• axial length
• school myopia

Abbreviations

AL, axial length; ACD, anterior chamber depth; LT, lens thickness; TALE, the total AL elongation; GRC, growth rate change.

Statement of Ethics

All of the procedures used conformed to the tenets of the Declaration of Helsinki, and they were approved by the Ethics Committee of Kagoshima University Hospital. A written informed assent and informed consent were obtained from all subjects and their parents. This study was registered with the University Hospital Medical Network-clinical trials registry (No. UMIN000015239).

Disclosure

Dr Takehiro Yamashita reports grants from Alcon and Novartis, outside the submitted work. The authors declare that they have no other conflicts of interest.

Additional information

Funding

The funding organizations had no role in the design or conduct of this research. This study was supported by JSPS KAKENHI grant number 21H03095, 21K09704 and Suda memorial glaucoma research grant.