Axial length for 7-8 years pupils of in Southern China

ABSTRACT

Purpose

To assess eye axial length (AL), spherical equivalent (SE), astigmatic power, distance unaided visual acuity (UCVA), and their relationship in 7- and 8-year-old pupils in Kunming, Southern China.

Methods

Grade I and grade II pupils underwent measurement of AL, UCVA, and refraction. The associations of AL with SE, UCVA and astigmatic power were studied.

Results

Two hundred ninety one pupils enrolled with 50.2% girls. AL was 22.71 ± 0.61 mm in children with emmetropia (UCVA > 0.8, –0.50 < SE < +0.50D and astigmatism < 0.50D), it was 23.46 ± 2.42 mm in children with mild myopia (–1 ≤ SE < –0.50D and astigmatism < 0.50D), it was 23.96 ± 1.16 mm in children with myopia (SE < –1D and astigmatism < 0.50D), and it was 22.20 ± 1.16 mm in children with astigmatism (astigmatism ≥ 0.50D). AL was highly related to SE (r = 0.572, P < .0001) with the formula AL = 22.45–0.59*SE.

Conclusion

In these 7- to 8-year old pupils, average AL was 22.88 ± 0.09 mm and average SE was –0.75 ± 0.13D. Astigmatic eyes demonstrated relative shorter AL while severe myopic eyes had the longest AL, although both had worse UCVA. One mm extra axial length corresponded to –1.69D extra myopia for 7- and 8-year-old pupils in Southern China.

KEYWORDS:

• Axial length
• emmetropia
• myopia
• astigmatism
• refractive error

Declarations

This study was approved by the institutional review board and ethnic committee at the University of Kunming Medical School. Written informed consent was obtained from the supervisors and participants. There were no competing conflicts of interest. All authors consent to publication with full available data and materials.