The aim of this study was to compare the differences of visual impairment rate and ocular biological parameters among 13 to 16 years old adolescents of different nationalities in Baotou city of Inner Mongolia Autonomous Region.

From November 2019 to April 2021, 1326 middle school students (2652 eyes) aged 13 to 16 years-old with an average age of (14.3±1.1) years-old in Baotou City were selected. Among them, according to ethnic nationality, they were divided into Han nationality, Mongolian nationality, Hui nationality, Manchu nationality and Daur nationality. The visual acuity, anterior segment, eye position, fundus and diopter examination were performed. The keratometry (K), anterior chamber depth (ACD), lens thickness (LT) and axial length (AL) were measured using Lenstar900 optical biometric instrument. The naked vision below 0.8 was considered as poor vision. The spherical equivalent refraction less than -0.50 D was considered as myopia. The number of poor vision, myopia and farsightedness was described by cases and pertentage and compared using χ² test. K, ACD, LT and AL of students were countable quantity, described by ±s , and compared using one-way ANOVA among groups. When there was a statistical difference among groups using one-way ANOVA, LSD was used for further comparison.

Among of the eligible students, the poor eyesight rate of Han nationality, Mongolian nationality, Hui nationality, Manchu nationality and Daur nationality students were 64.5%, 56.6%, 56.3%, 58.0% and 52.6%, respectively. There was significant different in the poor eyesight rate among all ethnic groups (χ²=9.642, P<0.05). The prevalence of hyperopia was 6.8% for Han nationality, 6.9% for Mongolian nationality, 6.3% for Hui nationality, 7.1% for Manchu nationality and 7.7% for Daur nationality. The difference had not statistical significance in the prevalence of hyperopia among ethnic groups (χ²=0.160, P>0.05). The prevalence of myopia of students was 57.6% for Han nationality, 49.7% for Mongolian nationality, 50.0% for Hui nationality, 50.9% for Manchu nationality and 44.9% for Daur nationality. There was a statistically significant difference in the prevalence of myopia among all ethnic groups (χ²=9.581, P<0.05). K of Han nationality, Mongolian nationality, Hui nationality, Manchu nationality and Daur nationality students was (44.10±1.11)D, (42.49±0.80)D, (42.27±1.38)D, (42.69±0.98)D and (42.88±1.26)D, respectively. The difference had statistical significance in K among all ethnic groups (F=4.026, P<0.05). The difference had statistical significance in K among Han nationality, Mongolian nationality, Hui nationality, Manchu nationality and Daur nationality students after LSD analysis (t=3.194, 3.627, 2.793, 2.435; P<0.05). ACD of Han nationality, Mongolian nationality, Hui nationality, Manchu nationality and Daur nationality students were (3.38±0.19)mm, (3.28±0.13)mm, (3.41±0.18)mm, (3.25±0.13)mm and (3.30±0.12)mm, respectively. The difference had not statistical significance in ACD among all ethnic groups (F=2.053, P>0.05). LT of Han nationality, Mongolian nationality, Hui nationality, Manchu nationality and Daur nationality students were (3.33±0.17)mm, (3.34±0.22)mm, (3.22±0.11)mm, (3.25±0.14)mm and (3.35±0.18)mm, respectively. The difference had not statistical significance in LT among all ethnic groups (F=1.211, P>0.05). AL of Han nationality, Mongolian nationality, Hui nationality, Manchu nationality and Daur nationality students were (25.14±0.72)mm, (23.33±1.17)mm, (25.00±0.96)mm, (24.89±1.28)mm and (23.38±0.74)mm, respectively. There was significant different in AL among all ethnic groups (F=8.309, P<0.05). There were significant different in AL among Han nationality, Mongolian nationality and Daur nationality studnets after LSD analysis (t=4.063, 3.934; P<0.05). The differences had not statistical significance in AL among Han nationality, Hui nationality and Manchu nationality studnets (t=0.313, 0.579; P>0.05).

Myopia is the main cause of poor eyesight among adolescents in Baotou City, Inner Mongolia Autonomous Region. The rate of poor eyesight of ethnic minorities adolescents is lower than that of Han nationality. AL and K are the main factors affecting refractive status.