Objective: To investigate the incidence and features of myopia in children aged 7 to 14 years.
Methods: Cross-sectional study. A total of 2 226 children (2 226 eyes) aged 7 to 14 years were selected from school during June 2012 and January 2015. Refraction was measured by fast cycloplegic retinoscopy. SPSS16.0 was used to analyze the data. Ocular refractive parameters, including axial length (AL), corneal power, anterior chamber depth, and white to white, were measured by IOLMaster (version 5.0, Carl Zeiss, Germany). Only the right eyes were included in the analysis.
Results: (1) The incidence of myopia in children increased with age. The incidence of myopia in female children was higher than male children with the same age. The overall incidence of myopia in female children was higher than male children (χ(2)=4.284, P=0.036). The average AL was (23.53±1.12) mm in male children and (23.44±1.08) mm in female children, and there was no statistically significant difference (t=1.502, P=0.134). (2) The change of refractive parameters was as follows. The AL elongated with age ,the average AL located in (22.84±0.87) to (24.49±1.19) mm(F=10.076, P<0.001) . The anterior chamber became deepened with age,the average ACD located in (3.28±0.16) to (3.67±0.24) mm (F=8.059, P<0.001). The white to white reduced slightly with age, the average WTW located in (12.30 ± 0.35) to (12.16 ± 0.54) mm,although there was no significant difference (F=0.469, P=0.857). There was no difference in the corneal power with age ,the average corneal power located in (43.05±1.31) to (43.74±1.20) D(F=0.440, P=0.877). The values of AL, anterior chamber depth in the myopia group were greater than the emmetropia group with the same age (P<0.05). (3) Correlation factor analysis of AL was as follows. Mixed effects model displayed that the age, height, and body weight were related to eye axis. The regression equation of AL was: AL=19.120 4+0.124 2×A+0.019 6×H+ 0.015 3×W. The AL was positively correlated with the body height (r=0.527, P< 0.01) and weight (r=0.47, P< 0.01).
Conclusions: Among children aged 7 to 14 years, the incidence of myopia, AL, and anterior chamber depth increase with age. During the period of rapid physical development, the refraction and AL should be monitored. The prevalence of myopia is relatively high in girls, which may be associated with outdoor activity. (Chin J Ophthalmol, 2016, 52: 514-519).