Prevalence and inconformity of refractive errors and ocular biometry of 3573 medical university freshman students for 4 consecutive years

INTRODUCTION

CR is the main clinical endophenotype of the refractive status.A more negative or myopic refractive error is associated with a steeper CR. Approximately 35%-95% inter-individual CR variation is associated with genetic factors

. In line with our results, among the adult Egyptian population with myopia,with the increase of myopic diopter, the cornea became steeper

. The LT is changing in one’s life. Children with myopia first showed a pattern of lens thinning, between the age of 10 and 11.5y, the lens reaching thinnest, after 18 years old, it becomes thicken until 75 years old

. The increase in LT could cause myopia drift. For example, in patients with diabetes, glucose may accumulate in the lens, with an increase in curvature and thickness and a shift toward myopia

. Shih

reported that a thinner LT can have an emmetropization effect and may be associated with increased AL, possibly playing a role in myopia progression. However, in 6-18-yearold teenagers, course myopia and lens thickening and thinning association was considered coincidental

. CCT is highly hereditary and is associated with complex eye diseases, such as glaucoma and keratoconus

. Chen

and Sun

reported that CCT was an independent factor, and was not associated with CR, ACD, AL, or refractive error. In our study,the CCT difference was not statistically significant, which was consistent with the results of Chen

’s

study.

Ocular biometric parameters are important for the evaluation of myopia. There is a strong association between ocular biometric parameters and refraction

. Based on refractive status and sex, for the main ocular biometric parameters in young adults,Sun

provided a range of reference values. However,data on ocular biometry remain scarce in medical university students. Axial length (AL) contributes to the variance in spherical equivalent (SE)

. High myopia is usually defined as an AL≥26.0 mm or an SE more than 6.0 D

. High myopia associated with cataracts, myopic glaucoma, or myopic macular degeneration is one of the leading causes of blindness,particularly in European and East Asian countries

.

为确保《意见》有效落实，云南省高院将制定具体方案，将《意见》进一步细化分解，明确任务分工、责任部门和责任人，确保这项工作有人抓、有人管，有人去落实。组织一线法官认真学习领会，切实把文件的精神落实到具体案件的办理过程始终，让人民群众有看得见、摸得着的切身感受，努力做到让人民群众在每一个司法案件中感受到公平正义。加强对《意见》实施的督促检查以及实施效果的跟踪分析研判，提高对全省法院审判业务指导的针对性和实用性，强化《意见》落实效果。

(2)M=m′∪Part∪Component∪Element，其中：Part表示部件节点的集合，Component表示组件节点的集合，Element表示零件节点的集合。整机由多个部件组成，部件由多个组件和零件组成，组件又由多个零件组成。

SUBJECTS AND METHODS

This study adhered to the tenets of the Declaration of Helsinki and was approved by the Ethics Committee of Tianjin Medical University Eye Hospital(No.2021KY-16). Before the study, all participating students signed an informed consent form.

随着经济的发展、城镇化水平的提高，人们会向大城市聚集，往往伴随着生育率的下降。比如过去广东的生育率一直很高，但随着城镇化水平的提高，以及珠江三角洲的快速发展，越来越多的人们开始涌向深广这些发达城市，随之而来的就是出生率的下降。这是因为大城市房价上涨过快，生活成本更高，会带来生育的负担，高房价等经济压力正在越来越影响人们的生育决策[4]。所以城镇化的发展也会在一定程度上影响人口老龄化的进程。

This study was conducted at Tianjin Medical University, China. From 2017 to 2020, 3895 freshman students were invited to participate in this study. Students originated from all provinces of mainland China. Undergraduates who unwilling to cooperate with examination, without successful biometric measurements (

=299), glaucoma (

=2), undergone retinal detachment surgery (

=6) or refractive surgery (

=15)were excluded. Eventually, effective ocular biometric data were obtained for 3573 (91.73%) students in this study.

The examination included distant visual acuity, ocular biometry, and non-cycloplegic refraction.An optical biometer (LENSTAR LS900, i8.2.2.0, Haag-Streit, Koeniz, Switzerland) was used to measure the central corneal thickness (CCT), AL, keratometry power (K),anterior chamber depth (ACD), and lens thickness (LT). Five repeated measurements were taken, and the average value was calculated for each parameter. Non-cycloplegic refraction was measured using an automatic refractometer (model KR 8900;Topcon, Tokyo, Japan) by professional optometrists, and after three measurements, refractive errors [spherical (S), cylinder(C), axis (A)] were recorded.

Refractive errors were classified according to SE. The SE was calculated using the following equation:SE=S+C/2. Emmetropes were defined as SE between -0.5 and +0.5 D. Myopia was defined as an SE＜-0.50 D, whereas hyperopia was defined as an SE＞0.50 D. Myopia was also classified into high, moderate, and mild myopia, based on an SE of ＜-6.00, -3.00 to -6.00, and -0.50 to -3.00 D, respectively.Different criteria were also used to define the extent of astigmatism (cylinder powers 0.50-＜0.75, 0.75-＜1.00, and≥1.00 D). Total astigmatism (TA) refers to the astigmatism of the eye as a complete ocular system. TA was the combined outcome of internal astigmatism (IA) and corneal astigmatism(CA). TA and CA were obtained from the measurement of automatic refractometer and lenstar, using the following formula IA=TA-CA. A cylinder axis of 90°±30° was defined as against-the-rule (ATR) astigmatism, a cylinder axis of 180°±30° was defined as with-the-rule (WTR) astigmatism,and cylinder axis of 31°-59° or 121°-149° was defined as oblique astigmatism. The cylinder power was expressed in the form of a negative. Corneal radius (CR) was extracted from the K value using the formula CR (mm)=1000×0.3375/K (D).The ACD was defined as the distance from the anterior lens to the corneal endothelium. The corrected lens position (LP) was defined as the sum of half of the LT, and the ACD

.

This study investigated the prevalence of refractive errors and determined the distribution of ocular biometric parameters in freshman students at Tianjin Medical University.

3.药物不良反应观察：抗病毒药物的不良反应及耐受性影响患者的服药依从性，进而影响抗病毒治疗的成败，所以适时监测并及时处理药物的不良反应对于提高治疗效果至关重要（表 7）。

RESULTS

This study comprised 3573 [1312 (36.7%) males and 2261 (63.3%) females]students. The mean age was 18.22±0.67y (range: 15-23y).The total prevalence of hyperopia, emmetropia, myopia was 1.3%, 3.7%, 95%, and prevalence of mild myopia, moderate myopia, high myopia was 23.9%, 43.6%, and 27.5%. There was no statistically significant difference between males and females. The prevalence of myopia from 2017 to 2020 were 93.5%, 94.5%, 95.9%, and 96.2%, respectively (

=0.03). The prevalence of high myopia was 25.7%, 26.9%, and 28.6%,respectively. The prevalence of high myopia increased in the first 3 years, while the difference was not statistically significant (

=0.45; Table 1).

For myopic subjects with AL＜26 mm, the group with high myopia had a longer AL, lower CCT, andsteeper CR than the group with mild to moderate myopia.For myopic subjects with AL≥26 mm, the group with mild to moderate myopia had shorter AL, flatter CR, and thinner LT than the group with high myopia (Table 5).

Statistical Package for the Social Sciences(SPSS) statistical package version 20.0 (IBM Corporation,Armonk, NY, USA) was used to perform statistical analysis.There was no significant difference in the number, sex, and age in each year; thus, freshman students’ data from 4 consecutive years were analyzed together. For continuous variables, data are presented as mean±standard deviation (SD). Categorical variables were compared for the different groups using the Chi-squared test. Continuous variables were assessed using the analysis of variance and compared using an independent

-test.Only the right eye was analyzed.

-values were two-sided and considered significant at

＜0.05.

Astigmatism was generally set at 1.00 D as a clinically significant threshold. The most common type of TA was WTR(90.3%), followed by ATR (5.8%) and oblique astigmatism(3.9%). However, there were no significant differences between males and females (Table 3).

兰德通过商业管理创新来帮助美国军事物流实现现代化，这些研究为国防部节省了数百万美元，同时提高了军队战斗力。

With diopters increase in myopia, the AL became longer, LT became thinner, CR became steeper, ACD became deeper, and LP became posterior(all

＜0.01). CCT did not change statistically significantly(

=0.10). Females were found to have a shorter AL, thinner CCT, smaller CR, shallower ACD, thicker lens, and more anterior LP than males (

＜0.01). SE was not statistically significant between males and females (

=0.11; Table 4).

This work describes refractive errors prevalence and ocular biometry in 3573 freshman students at Tianjin Medical University for 4 consecutive years. Our results showed that the prevalence of myopia and high myopia increased annually. Huang

reported that myopia prevalence among university students in Nanjing was 86.8%. Sun

conducted a cross-sectional study on 5060 students in Donghua University in Shanghai, a developed city in China,and observed the mean refractive error was -4.1 D and the prevalence of myopia and high myopia was 95.5% and 19.5%,respectively. Lv and Zhang

reported that the prevalence rate of myopia increased significantly from 78.5% to 84.1%in students in Weifang Medical College, with a mean age of 18.27y over a 2-year follow-up study in 2008 and 2010.The prevalence of myopia was 70.5% and 69.2% at Inner Mongolia Medical University in 2011 and 2013, which was an underdeveloped inland city in North China

. Our results were consistent with Donghua University in Shanghai and Nanjing but were significantly higher than those in Weifang Medical College and Inner Mongolia Medical University. Probably because myopia is associated with economic levels

.

Males tended to have a higher percentage of TA than females with astigmatism 0.75-＜1.00 and ≥1.0 D, females tended to have a higher percentage of CA and IA with astigmatism ≥0.75 D(Table 2).

1.3.1 冠脉造影所示IRA前向血流情况。IRA前向血流定义：TIMI 3级或TIMI2级为有前向血流；TIMI 0级或TIMI 1级为无前向血流。

DISCUSSION

According to AL, individuals with myopia were divided into two groups: AL≥26 mm and AL＜26 mm. The 36% of high myopia had AL＜26 mm, 78.9%moderate myopia, and 94.2% mild myopia had AL＜26 mm.The 64% of high myopia had AL≥26 mm. Meanwhile, 5.8%mild myopia and 21.1% moderate myopia had AL≥26 mm(Figure 1).

CA refers to astigmatism on the anterior surface. IA is difficult to measure, thus, it is usually considered to be the difference between TA and CA

. The percentage of those with TA≥0.50 D(64.8%) was lower than that of those with CA (88.1%), which is consistent with Chen

’s

results because IA usually has a compensatory association with CA. Males tended to have a higher percentage of TA than females with astigmatism≥0.75 D and ≥1.0 D; however, females tended to have a higher percentage of CA and IA with astigmatism ≥0.75 D. WTR astigmatism was the main type of astigmatism.

In our study, AL (25.28±1.24 mm) was longer than university students in Shanghai (male: 25.10±1.55 mm, female:24.74±1.49 mm)

and Anyang (24.78±1.21 mm)

. In our opinion, this was associated with higher diopter. Females had a shorter AL, thinner CCT, smaller CR, shallower ACD, thicker lens, and more anterior LP than males, which was consistent with previous studies results of young adults

, children

.With the diopters increase in myopia, the AL became longer,CR became steeper, ACD became deeper, LT became thinner,and LP became posterior, which was consistent with Anyang study results.

Myopia has become a global public health problem.Recent Meta-analyses have suggested that by 2050,approximately 49.8% of the world population will have myopia,and 9.8% of the world population will have high myopia

. In developed countries in Southeast and East Asia, the prevalence of myopia is currently 80%-90% in children completing secondary schooling (age 17-18y)

. In China, Sun

reported that in Dong Hua University in Shanghai, 19.5% and 95.5% of freshman students had high myopia and myopia,respectively, and Wang

reported that approximately 90% and 26% of high school students in eastern China had myopia and high myopia, respectively. Lv and Zhang

reported that the prevalence of myopia in medical university students increased from 78.5% to 84.1% over a 2-year followup period. Adolescent myopia, particularly among university students

, has become a marked public health problem.Astigmatism is a common type of refractive error, defined as the difference between the two principal meridians of the eyeball in refractive error

.

We divided students into groups according to AL. In 3395 students with myopia, 64% of high myopia had AL≥26 mm,but we also found that 5.8% of mild myopia and 21.1% of moderate myopia had AL≥26 mm. In myopia students with AL≥26 mm, mild and moderate myopia compared to high myopia, AL was shorter (26.51±0.46

26.87±0.70 mm),CR was larger (8.10±0.30

7.85±0.23 mm) and LT was thinner (3.39±0.19

3.45±0.19 mm;

＜0.001). The larger CR and thinner LT neutralize the longer AL and manifest mild or moderate myopia. It is known that the longer the AL,the higher the risk of fundus lesions. The axial elongation has been associated with maculopathies and resulted in degenerative changes in the retina, such as macular holes

,posterior staphyloma

, retinal pigment epithelium atrophy,and choroidal neovascularization

. The prevalence rate of myopic macular degeneration in subjects with an AL≥26 mm was higher than that in subjects with an AL＜26 mm

. Therefore,inconformity of refractive errors and ocular biometry existed in some students. Therefore, attention should be paid to the ocular biometry of myopia.

This study had some limitations. First, we may overestimate the prevalence of myopia without cycloplegia, a study showed that a mean 0.4±0.5 D hyperopic shift after cycloplegia aged 10-40y

. Hence, future studies regarding cycloplegia should be conducted. Second, the subjects were recruited from one medical university. Thus, the generalization of our findings to Chinese young adults should be cautious.

In summary, the prevalence rates of myopia, high myopia were significantly high among freshman students at Tianjin Medical University. Inconformity of refractive errors and ocular biometry existed in some students. More attention should be paid to the ocular biometry of mild and moderate myopia.

We would thank all those participants who contributed to this study.

今年A股市场震荡回落，三大指数屡创阶段新低，估值水平处于历史低位。展望2019年，养老目标基金、职业年金、外资等长线资金将给市场带来更多的增量资金，有助于提高资本市场的稳健性和有效性。

Supported by the Science & Technology Development Fund of Tianjin Education Commission for Higher Education of China (No.2018KJ056).

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