The aim of this study was to assess the impact of monocular myopic anisometropia on the refractive parameters of children′s eyes and analyze the correlation between axial changes and refractive changes.

From July 2017 to May 2020, 70 cases (140 eyes) of children with monocular myopic anisometropia were collected from the Eye Center of Beijing Tongren Hospital affiliated to Capital Medical University. Among them, there were 28 males (56 eyes) and 42 females (84 eyes), aged 8 to 15 years with an average age of (11.0±1.9) years. All patients were measured for axial length, corneal curvature flatness K value, corneal curvature steepness K value, corneal flatness E value, and corneal steepness E value. Astigmatic refraction and calculation of equivalent spherical diopter were performed. The patients′ age, axial length, equivalent spherical refractive index, D-value of axial length, D-value of refractive index, corneal curvature flatness K value, steep K value, corneal flatness E value, and steep E value conformed to a normal distribution, and were described by ±s. The biological parameters between healthy and affected eyes was compared using paired t testing. According to age range, they were divided into 8 to 10 years old group and 11 to 15 years old group. The correlation between D-value of binocular axial length and D-value of refractive index were performed Pearson correlation coefficient and linear regression analysis.

Among 70 patients (140 eyes), there were 28 males (56 eyes), accounting for 40%, and 42 females (84 eyes), accounting for 60%. There were 51 patients (51 eyes) with right myopia, accounting for 72.86%, and 19 patients (19 eyes) with left myopia, accounting for 27.14%. The axial length of the affected eye was (24.49±0.84) mm, while the axial length of the healthy eye was (23.54±0.73) mm. There were statistically significant differences between the two groups (t=15.626, P<0.05). The equivalent spherical diopter of the affected eye and the healthy eye was (-2.39±1.05) D and (-0.07±0.32) D, respectively. The difference between the two eyes was statistically significant (t=-18.214, P<0.05). The K value of corneal curvature flatness in the affected eye was (42.74±1.28), while the K value of corneal curvature flatness in the healthy eye was (42.75±1.29). There was no statistically significant difference between the two eyes (t=0.344, P>0.05). The K value of corneal curvature in the affected eye was (44.03±1.44), while the K value of corneal curvature in the healthy eye was (43.92±1.38). The difference between the two eyes was statistically significant (t=-3.392, P<0.05). The E value of corneal flatness in the affected eye was (0.64±0.09), while the E value of corneal flatness in the healthy eye was (0.66±0.11). The difference between the two eyes was statistically significant (t=2.672, P<0.05). The E value of corneal steepness in the affected eye was (0.50±0.20), while the E value of corneal steepness in the healthy eye was (0.53±0.20). There was no statistically significant difference between the two eyes (t=1.226, P>0.05). The differences in binocular axial length among patients in the overall, 8 to10 year old group, and 11 to15 year old group were (0.94±0.50) mm, (0.78±0.43) mm, and (1.07±0.52) mm, respectively. The differences in refractive power were divided into (-2.30±1.05) D, (-2.01±1.05) D, and (-2.66±1.00) D. The correlation between the differences in binocular axial length and refractive power in each group was statistically significant (r=-0.850, -0.835, -0.792; P<0.05). A univariate linear regression equation using the difference in binocular axial length and diopter was constructed, denoted by ŷ=- 1.788x-0.624, ŷ=- 2.054x-0.421, ŷ=- 1.53x-1.024, which suggesting that D-value of the myopia diopter would increase by -1.79 D if D-value of the axial length increased for every 1 mm in children aged 8 to 15 year old; D-value of the myopia diopter would increase by -2.05 D if D-value of the axial length increased for every 1 mm in children aged 8 to 10 year old; D-value of the myopia diopter would increase by -1.53 D if D-value of the axial length increased for every 1 mm in children aged 11 to 15 year old.

Anisometropia affects refractive parameters such as axial length, corneal curvature steepness K value, and corneal flatness E value. Axial growth is closely related to the growth of myopia. Every 1 mm increase in axial difference will cause 1.79 D refractive error change within the children aged between 8 to 15 years old.