Abstract:

Objective

The aim of this study is to assess the correlation between the changes of spherical equivalent and myopia progression in children with refractive error.

Methods

From January 2021 to December 2023，a total of 124 cases（248 eyes）of children and adolescents with refractive error were collected from the Eye Center of Beijing Tongren Hospital affiliated to Capital Medical University.Among them，there were 63 males（126 eyes）and 61 females（122 eyes）with an average age of（10.0±2.1）years（ranged from 6 to 15 years）.According to age，they were divided into 6 to 9 years old group，9 to 12 years old group and 12 to 15 years old group.According to the ratio axial length to spherical equivalent（AL/CR），they were divided into AL/CR＜3 group，3≤AL/CR≤3.2 group and AL/CR＞3.2 group.All patients were measured for axial length，corneal curvature flatness K value，and corneal curvature steepness K value by optical biometry.Spherical equivalent，AL/CR，SE change（ΔSE）and AL change（ΔAL）were measured and calculated by non-contact computer optometry.The detection rate of myopia was represented by percentages and compared usingχ² test.The patients'age，axial length，AL/CR，equivalent spherical diopter，corneal curvature，ΔAL、ΔSE andΔSE/ΔAL conformed to a normal distribution，and were described by.The parameters among the three groups were tested by one-way ANOVA.When the differences among three groups are statistically significant，two-by-two comparisons between the groups were made.The correlation betweenΔSE andΔAL were performed Pearson correlation coefficient and linear regression analysis.The validity of the linear regression equation was tested by ANOVA.

Results

A total of 124 children（248 eyes）were enrolled.The rate of myopia was 58% and the rate of hyperopia was 30%.The detection rate of myopia significantly increased with age and there was a significant difference between them（χ²=12.61，P＜0.05）.In 6 to 9 years old group，9 to 12 years old group and 12 to 15 years old group，the axial length（AL）of patients were（23.04±1.28）mm，（23.98±0.54）mm，and（24.44±1.18）mm.The AL/CR of patients were 2.90±0.20，3.04±0.20，and 3.08±0.17.The corneal curvature of patients were（43.63±1.72）D，（43.48±1.78）D，and（42.75±1.63）D.There were differences in AL and AL/CR among different age groups with statistically significant（F=20.37，13.75；P＜0.05），while the corneal curvature exhibited no significant differences（F=0.61，P＞0.05）.Linear regression equation was constructed with age as the independent variable andΔSE/ΔAL as the dependent variable，denoted by y=0.034x+1.448.After the validity analysis，there was a significant difference between them（F=3.949，P＜0.05）.Linear regression equation was constructed withΔAL as the independent variable andΔSE as the dependent variable in the overall and different age groups，denoted by y=0.034x+1.448.After the validity analysis，there was a significant difference between them（F=491.2，P＜0.05）.Among children in three age groups：6 to 9 years old，9 to 12 years old and 12 to 15 years old，the univariate linear regression equation was denoted by y=-1.472x-0.013、y=-1.617x-0.090 and y=-1.729x-0.025.The myopia progression would increase by-1.60 D if the axial length increased for every 1 mm in children aged 6 to 15 years old.Linear regression equation was constructed with ΔAL as the independent variable andΔSE as the dependent variable in different AL/CR groups，denoted by y=-1.490x-0.108，y=-1.642x-0.070 and y=-1.896x-0.059.The myopia progression would increase respectively by-1.49 D，-1.64 D and-1.90 D if the axial length increased for every 1 mm in different AL/CR groups（AL/CR＜3，3≤AL/CR≤3.2 and AL/CR＞3.2）.Pearson correlation analysis showed that the correlation between the differences inΔSE/ΔAL and AL/CR，ΔSE/ΔAL and AL was statistically significant（r=-0.208，-0.106；P＜0.05）.

Conclusions

The myopia progression is closely corelated to the axial length elongation in the children aged between 6 to 15 years old.The myopia progression would increase by-1.60 D if the axial length increased for every 1 mm.ΔSE/ΔAL is significantly corelated to age，AL/CR and axial length.The elongation of axial length can be used as a critical indicator to predict the development of refractive errors.

Key words: Diopter, Children, Axial length, Refractive errors