Prevalence of myopia in a group of Hong Kong microscopists.

PURPOSE: To study the prevalence and magnitude of myopia in a group of Hong Kong Chinese microscopists and compare it with that observed in microscopists working in the United Kingdom. METHODS: Forty-seven microscopists (36 women and 11 men) with a median age of 31 years and working in hospital laboratories throughout Hong Kong were recruited to the study. Information about past refractive corrections, microscopy work, and visual symptoms associated with microscope use were collected. All subjects had a comprehensive eye examination at The Hong Kong Polytechnic University Optometry Clinic, including measures of refractive error (both noncycloplegic and cycloplegic), binocular vision functions, and axial length. RESULTS: The prevalence of myopia in this group of microscopists was 87%, the mean (+/- SD) refractive error was -4.45 +/- 3.03 D and mean axial length was 25.13 +/- 1.52 mm. No correlation was found between refractive error and years spent working as a microscopist or number of hours per day spent performing microscopy. Subjects reporting myopia progression (N = 22) did not differ from the refractively stable group (N = 19) in terms of their microscopy working history, working hours, tonic accommodation level, or near phoria. However, the AC/A ratio of the progressing group was significantly greater than that of the stable group (4.59 delta/D cf. 3.34 delta/D). CONCLUSION: The myopia prevalence of Hong Kong Chinese microscopists was higher than that of microscopists in the United Kingdom (87% cf. 71%), as well as the Hong Kong general population (87% cf. 70%). The average amount of myopia was also higher in the Hong Kong Chinese microscopists than the Hong Kong general population (-4.45 D cf. -3.00 D). We have confirmed that the microscopy task may slightly exacerbate myopia development in Chinese people.     

Prevalence, incidence, and progression of myopia of school children in Hong Kong

PURPOSE: To determine the prevalence, incidence, and progression of myopia of Chinese children in Hong Kong. METHODS: A cross-sectional survey was initially conducted. A longitudinal follow-up study was then conducted 12 months later. RESULTS: A total of 7560 children of mean age 9.33 (95% confidence interval [CI] = 9.11-9.45; range, 5-16) participated in the study. Mean spherical equivalent refraction (SER) was -0.33 D (SD = 11.56; range, -13.13 to +14.25 D). Myopia (SER 相似文献   

Changes in refractive trends and optical components of Hong Kong Chinese aged 19–39 years

The distribution of refractive errors and its relationship to the optical components in 105 Hong Kong Chinese aged 19–39 years was studied. Myopia was most frequent (71%) in this population. The mean spherical equivalent was -3.00 DS. The trend of changes of the direction of refractive and corneal astigmatism from with-the-rule to against-the-rule with increasing age was shown. Significant correlations were found between age and anterior segment distance. Ultrasound examination showed that an increasing axial length was associated with higher myopia. Men had flatter corneal radii, but longer axial length. The prevalence of myopia in the Chinese population seems to be a new trend for the younger Hong Kong Chinese when compared with adults aged over 40 years. Thus the importance of genetics in determination of myopia is called into question by these findings.     

Change in vision disorders among Hong Kong preschoolers in 10 years

Background: To determine the change in refractive error and the prevalence of amblyopia and strabismus among preschool children in Hong Kong over a period of 10 years. Design: Two cross‐sectional population‐based studies conducted in 1996 to 1997 (part A) and 2006 to 2007 (part B) Participants: Children attending randomly selected kindergarten participated in the study. Methods: Ocular alignment, visual acuity, cover and uncover tests, cycloplegic refraction, slit‐lamp and fundi examination were performed under a standardized testing environment. Main Outcome Measures: The prevalence of amblyopia (best‐corrected visual acuity ≤6/12 in one or both eyes, or a bilateral difference of ≥2 best‐corrected visual acuity lines), strabismus and significant refractive error (hyperopia ≥+2.50 D; myopia ≥?1.00 D; astigmatism ≥2.00 D) among preschool children. Results: Of the 601 children in part A of the study, reduced visual acuity was presented in 3.8%; whereas strabismus was found in 1.8%. The commonest type of refractive error was astigmatism in 6.3% of children, followed by hyperopia (5.8%) and myopia (2.3%). Among 823 children in part B, reduced visual acuity was presented in 2.7% of children, and strabismus was found in 1.7%. The commonest type of refractive error was myopia (6.3%), followed by astigmatism (5.7%) and hyperopia (5.1%). The percentage of children having myopia has significantly increased (P = 0.001). Conclusion: A significant increase in myopia has been noted in Hong Kong preschoolers. Visual screening programmes may need to be tailored to correspond to the local population and be adjusted accordingly from time to time.     

Effect of parental myopia on the development of myopia in Hong Kong Chinese

A representative sample of Hong Kong Chinese children was followed from 7 to 12 years of age. Refractive error was measured every year (n = 123 at age 7 years and n = 83 at age 12 years), the axial length of the eye was measured at age 12 years (n = 81) and the refractive status of the parents was also determined. Thirty-one percent of the parents in the sample were myopic and at the age of 12 years 53% of the children were myopic. There was no association between the refractive status of the parents and whether or not a child had myopia. The probability of a 12-year-old child with early-onset myopia having at least one myopic parent was 0.55 and the probability of myopic parents having a myopic child was 0.6. There was no difference in the refractive error or the axial length of 12-year-old children according to whether neither, one or both parents were myopic. The genetic influence on myopia may be different in Caucasian and Chinese children, although it is also possible that non-expression of the genotype in the parents may have confounded the determination of the inheritance pattern of myopia in Hong Kong Chinese children.     

Myopia prevalence in Chinese-Canadian children in an optometric practice.

PURPOSE: The high prevalence of myopia in Chinese children living in urban East Asian countries such as Hong Kong, Taiwan, and China has been well documented. However, it is not clear whether the prevalence of myopia would be similarly high for this group of children if they were living in a Western country. This study aims to determine the prevalence and progression of myopia in ethnic Chinese children living in Canada. METHODS: Right eye refraction data of Chinese-Canadian children aged 6 to 12 years were collated from the 2003 clinical records of an optometric practice in Mississauga, Ontario, Canada. Myopia was defined as a spherical equivalent refraction (SER) equal or less than -0.50 D. The prevalence of myopia and refractive error distribution in children of different ages and the magnitude of refractive error shifts over the preceding 8 years were determined. Data were adjusted for potential biases in the clinic sample. A questionnaire was administered to 300 Chinese and 300 Caucasian children randomly selected from the clinic records to study lifestyle issues that may impact on myopia development. RESULTS: Optometric records of 1468 children were analyzed (729 boys and 739 girls). The clinic bias adjusted prevalence of myopia increased from 22.4% at age 6 to 64.1% at age 12 and concurrently the portion of the children that were emmetropic (refraction between -0.25 and +0.75 D) decreased (68.6% at 6 years to 27.2% at 12 years). The highest incidence of myopia for both girls ( approximately 35%) and boys ( approximately 25%) occurred at 9 and 10 years of age. The average annual refractive shift for all children was -0.52+/-0.42 D and -0.90+/-0.40 D for just myopic children. The questionnaire revealed that these Chinese-Canadian children spent a greater amount of time performing near work and less time outdoors than did Caucasian-Canadian children. CONCLUSIONS: Ethnic Chinese children living in Canada develop myopia comparable in prevalence and magnitude to those living in urban East Asian countries. Recent migration of the children and their families to Canada does not appear to lower their myopia risk.     

The effect of having myopic parents: an analysis of myopia in three generations.

PURPOSE: The etiology of myopia has been attributed to both genetic and environmental factors. The purpose of this paper is to attempt to distinguish between genetic and environmental factors in three generations of subjects from three locations. METHODS: Noncycloplegic autorefraction and distance visual acuity were measured in 3131 Chinese children 7 to 17 years old from Hong Kong, Tianjin, and Ban Chau. Data on the refractive status of the parents and grandparents were collected using questionnaires. Myopia was defined operationally as spherical equivalent refractive error (SER) of at least -1.00 D and uncorrected vision worse than logMAR 0.18 (6/9). RESULTS: The odds of having myopia for the grandparents', parents', and children's generations were 0.06, 0.26, and 0.35, respectively. Having myopic parents increased the odds ratio for having myopia (odds ratio 1.85 for children's generation and 6.71 for parents' generation), showing a genetic influence. However, the odds of having myopia also increased in offspring of nonmyopic parents between generation 2 and 3, suggesting an environmental influence. Results of prevalence and odds ratios from the three locations also demonstrated an environmental effect on development of myopia. CONCLUSION: We propose that myopic development in Chinese follows a multifactorial and polygenic model in which the genetic input has remained constant while the environmental influence has increased over the last three generations.     

Myopia profile in Copenhagen medical students 1996-98. Refractive stability over a century is suggested

PURPOSE: To assess the myopia prevalence and profile in today's Danish medical students and to compare the pattern with previous and contemporary investigations. METHODS: As part of the tutoring in ophthalmology 1996-98 Copenhagen medical students of five successive terms (in their 10th semester, n=294) were interviewed and spot-checked about their refraction. Myopia from -0.5 D was recorded and myopia onset age stated. RESULTS: The age range was 22-41 years, median age 26. Myopia ranging from -0.5 to -8 D was encountered in 147 students (50% of all; females 53.9%, males 45%). In seven the myopia was unilateral. Median values for myopia degree and onset age were -2.5 D and 16 years in female myopes (n=89) which differed significantly from the male values (n=58) of -1.5 D and 18 years. Including the age of 18 as lower cut-off for adult-onset myopia 44.9% of the myopes belonged to this category. CONCLUSIONS: The results are in close agreement with recent Norwegian student investigations, and there is no obvious trend of a worsening of the academic myopia issue in our part of the world. This is in marked contrast to student myopia profiles as reported in Taiwan, Singapore, and Hong Kong where myopia is booming, by number and degree.     

Occurrence of myopia among Polish students aged 6 to 18 years old

PURPOSE: To determine the prevalence of myopia among students ranging from 6 to 18 years of age. MATERIAL AND METHODS: 5023 students in all, from elementary schools, junior high schools and high schools, aged 6-18 years were examined. Measurements of visual acuity as well as retinoscopy after cycloplegia have been carried out. The data was analysed using chi-square test. RESULTS: It was found that 15% of the students, aged from 6 to 18 suffers from myopia. It has been observed that from the sixth to the eighteenth years of life along with the age grows the prevalence was well as value of myopia. A major increase in the frequency of myopia occurrence among students over the age of 14 has been found. Significant differences between prevalence of myopia among boys and girls was not observed. CONCLUSIONS: (1) 15% of students in the age from 6 to 18 suffer from myopia. (2) Along with the age the prevalence of myopia increases.     

厦门地区城市与农村儿童近距离用眼与近视的关系

目的 :调查中国厦门城市与农村 8～ 9岁儿童近视的患病情况 ,并以此评估环境因素对近视患病率的影响。方法 :对中国厦门城市 (n =119)和农村 (n =91)的小学二年级学生进行散瞳电脑验光和眼生物参数测量 ,并采用同一标准的调查表进行面对面地问卷调查 ,内容包括社会经济地位、近距离用眼活动情况、读写习惯、近视眼家族史等。结果 :近视的发病率在城市为 19.3% [95 %可信区间confidenceinterval(CI) :12 .3,2 9],在农村是 6 .6 % (95 %CI:2 .4 ,14 .3)。城市在校学生每天课外读写平均时间是 2 .2h ,农村学生的收稿日期 :2 0 0 2 -0 3 -14 ;修回日期 :2 0 0 2 -0 5 -0 8基金项目 :新加坡政府及厦门开元区科委资助项目。作者简介 :张铭志 (195 7-) ,女 ,山东费县人 ,医学硕士 ,副主任医师。研究方向 :白内障、青光眼、近视。通信作者 :张铭志 (E -mail:fu- zhifu @hotmail.com)。时间是 1.6h(P <0 .0 0 1) ,所得结果经近视眼家族史因素校正后 ,总体读写时间比值比为 2 .2 (95 %CL :1.1,4 )。结论 :近视眼发病率 ,城市高于农村。城市儿童的课外读书时间比农村儿童长 ,城市和农村的近视儿童在读书上花费的时间明显高于非近视儿童。近距离用眼的增多可能导致了近视眼的发生 ,这为近距离用眼学说提供了更多依据     

Ametropia and ocular biometry in a U.K. university student population.

PURPOSE: The prevalence of myopia is known to vary with age, ethnicity, level of education, and socioeconomic status, with a high prevalence reported in university students and in people from East Asian countries. This study determines the prevalence of ametropia in a mixed ethnicity U.K. university student population and compares associated ocular biometric measures. METHODS: Refractive error and related ocular component data were collected on 373 first-year U.K. undergraduate students (mean age = 19.55 years +/- 2.99, range = 17-30 years) at the start of the academic year at Aston University, Birmingham, and the University of Bradford, West Yorkshire. The ethnic variation of the students was as follows: white 38.9%, British Asian 58.2%, Chinese 2.1%, and black 0.8%. Noncycloplegic refractive error was measured with an infrared open-field autorefractor, the Shin-Nippon NVision-K 5001 (Shin Nippon, Ryusyo Industrial Co. Ltd, Osaka, Japan). Myopia was defined as a mean spherical equivalent (MSE) less than or equal to -0.50 D. Hyperopia was defined as an MSE greater than or equal to +0.50 D. Axial length, corneal curvature, and anterior chamber depth were measured using the Zeiss IOLMaster (Carl Zeiss, Jena, GmBH). RESULTS: The analysis was carried out only for white and British Asian groups. The overall distribution of refractive error exhibited leptokurtosis, and prevalence levels were similar for white and British Asian (the predominant ethnic group) students across each ametropic group: myopia (50% vs. 53.4%), hyperopia (18.8% vs. 17.3%), and emmetropia (31.2% vs. 29.3%). There were no significant differences in the distribution of ametropia and biometric components between white and British Asian samples. CONCLUSION: The absence of a significant difference in refractive error and ocular components between white and British Asian students exposed to the same educational system is of interest. However, it is clear that a further study incorporating formal epidemiologic methods of analysis is required to address adequately the recent proposal that juvenile myopia develops principally from "myopiagenic" environments and is relatively independent of ethnicity.     

Nearwork-induced transient myopia in preadolescent Hong Kong Chinese

PURPOSE: To compare the magnitude and time course of nearwork-induced transient myopia (NITM) in preadolescent Hong Kong Chinese myopes and emmetropes. METHOD: Forty-five Hong Kong Chinese children, 35 myopes and 10 emmetropes aged 6 to 12 years (median, 7.5), monocularly viewed a letter target through a Badal lens for 5 minutes at either 5.00- or 2.50-D accommodative demand, followed by 3 minutes of viewing the equivalent target at optical infinity. Accommodative responses were measured continuously with a modified, infrared, objective open-field autorefractor. Accommodative responses were also measured for a countercondition: viewing of a letter target for 5 minutes at optical infinity, followed by 3 minutes of viewing the target at a 5.00-D accommodative demand. The results were compared with tonic accommodation and both subject and family history of refractive error. RESULTS: Retinal-blur-driven NITM was significantly greater in Hong Kong Chinese children with myopic vision than in the emmetropes after both near tasks, but showed no significant dose effect. The NITM was still evident 3 minutes after viewing the 5.00-D near task for 5 minutes. The magnitude of NITM correlated with the accommodative drift after viewing a distant target for more than 4 minutes, but was unrelated to the subjects' or family history of refractive error. CONCLUSIONS: In a preadolescent ethnic population with known predisposition to myopia, there is a significant posttask blur-driven accommodative NITM, which is sustained for longer than has previously been found in white adults.     

上海市宝山区5000名学生视力监测与干预情况

目的:通过监测获得宝山区中小学生视力、屈光不良情况,研究行为干预对近视发展有无影响。方法:采用整群随机抽样的方法,在上海市宝山区抽取中小学校5所,参照《眼科全书》近视诊断标准对所有学生进行视力普查,对视力低常学生使用拓普康RA800型验光仪进行电脑验光,选择基础条件相似的两所学校部分班级进行分组,加以行为干预,0.5a后对所测学生进行复查。结果:宝山区学生视力不良率高于上海市平均水平,且随年级升高呈现出阶梯性增长态势。小学生视力不良率已经达到将近50%,初中生达到了70%以上。随着年级增高,轻度屈光不良所占比例越来越低,重度屈光不良所占比例也越来越高,从一年级的10%左右增长到初二年级的30%左右。每个年级监测人群前后两次视力不良对比无统计学差异,每个年级屈光不良分级构成比前后无统计学差异。不能认为采取的干预措施对学生视力不良率的发展产生作用,但是干预对学生护眼知识方面水平的提高比较明显。结论:学生视力不良率随年级升高而逐渐升高,重度屈光不良所占比例也逐渐升高,强化行为干预对限制学生近视发展无明显作用。     

Refractive errors in an elderly Chinese population in Taiwan: the Shihpai Eye Study

PURPOSE: Few epidemiologic data are available on refractive status in elderly Asians. The purpose of the study was to determine prevalence and risk factors associated with refractive errors in a metropolitan elderly Chinese population in Taiwan. METHODS: A population-based survey was conducted in the Shihpai district of Taipei, Taiwan. A total of 2045 residents aged 65 years or more were randomly selected and invited to complete a comprehensive questionnaire and undertake a detailed ocular examination, including best corrected visual acuity and measurements of refractive error, using autorefraction. Of the subjects, 1361 (66.6%) participated in the ocular examination. Spherical equivalent (SE) was calculated in diopters (D), and data from right eyes were reported. RESULTS: The age- and sex-adjusted prevalence rates were determined for myopia (SE<-0.5 D, 19.4%; SE<-1.0 D, 14.5%), high myopia (SE<-6.0 D, 2.4%), hyperopia (SE>+0.5 D, 59.0%; SE>+1.0 D, 44.2%), astigmatism (cylinder<-0.5 D, 74.0%; cylinder<-1.0 D, 45.3%), and anisometropia (SE difference between right and left eyes>0.5 D, 45.2%; SE difference>1.0 D, 21.8%). The prevalence of myopia, astigmatism, and anisometropia significantly increased with age (all P<0.01). The prevalence of hyperopia tended to decrease with age. There was no gender difference in prevalence rates in any type of refractive error, except that women had a higher rate of hyperopia (SE>+1.0 D) than men (P=0.004). Multivariate regression analysis showed that myopia was weakly associated with higher educational level. The severity of lens nuclear opacity was positively associated with the rates of myopia and negatively associated with the rates of hyperopia. CONCLUSIONS: The prevalence of myopia in this elderly Chinese population is not much higher than in similarly aged elderly white populations, compared with a much greater difference in prevalence among younger Chinese versus white people. This suggests that changing environmental factors may account for the increased prevalence of myopia in younger cohorts of Chinese.     

山东省龙口市7～18岁中小学生近视患病率调查分析

目的：调查研究山东省龙口市7～18岁中小学生近视患病率情况,为近视防控提供科学依据。

方法：采用横断面随机整群抽样的方法于2015-01/12对山东省龙口市7～18岁在校学生以学校为抽样单位进行近视情况的调查,共抽取学校58所,有效抽样61 036人。按地域分为城市、城乡结合部及农村3类地区。由相关工作人员在全程质量控制下采用标准对数视力表检查受检者双眼裸眼视力,采用自动验光仪(TOPCON-RM8900)在非散瞳情况下行电脑验光检查。采用Microsoft Excel工作表建立数据库,SPSS 21.0软件进行统计学分析。

结果：2015年龙口市7～18岁中小学生的总体近视患病率为49.81%,11～12岁时总体近视患病率增幅最快,13岁时轻度近视患病率最高。男性和女性总体近视患病率分别为46.41%、53.39%,女性总体近视患病率高于男性。城市、城乡结合部及农村地区学生总体近视患病率分别为55.18%、49.75%、44.47%,城市学生总体近视患病率明显高于城乡结合部及农村地区。总体近视患病率与年龄呈正相关(r_s=0.943,P<0.05),即总体近视患病率随年龄的增长而逐渐升高。

结论：山东省龙口市2015年中小学生近视患病率较高,且随年龄的增长而逐渐升高,女性高于男性,城市高于城乡结合部及农村地区。     

The incidence of refractive errors among school children in Hong Kong and its relationship with the optical components

This study aims to provide information about the prevalence of refractive errors among Chinese school children in Hong Kong, and its relationship with the optical components of the eye. Subjective refraction, corneal curvatures and ocular biometry were performed on 383 school children from age six to 17 years. The prevalence of myopia increases from 30 per cent at age six to seven to 50 per cent (girls) and 70 per cent (boys) at age 16–17. The mean spherical equivalent refraction gradually changes from plano at age six to seven to -2.00 D of myopia at age 1617. Our results are different from Caucasian data but comparable with those of other studies of Chinese in Asia. The increase in myopia correlates well with the axial length of the eye. Further studies are needed to investigate the cause for the development of myopia.     

2018～2020年成都市新都区小学生近视流行病学研究

目的:观察新冠疫情居家隔离期(2020-01/05)前后成都市新都区小学生的近视流行病学特点。方法:横断面研究。采用随机分层整群抽样的调查方法,连续3a(2018~2020年)抽取成都市新都区4所小学的一年级到六年级学生(6~13岁),每个年级3个班共10153人,对纳入对象行视力检查及电脑验光,视力<5.0则进行散瞳验光,记录等效球镜度(SE),并计算各年龄组近视患病率。采用卡方检验比较不同年度近视患病率的差异,单因素方差分析比较不同年度SE的差异。结果:2018、2019、2020年近视患病率分别为35.98%、36.29%、42.52%(χ²=39.374,P<0.001)。6~9岁组学生2020年近视患病率明显提高(P<0.01),分别为2019年的2.20倍(6岁)、2.08倍(7岁)、1.36倍(8岁)、1.24倍(9岁)。6~9岁组学生2020年SE出现明显近视化(P<0.05),比2019年分别增长-0.34±0.76D(6岁)、-0.28±0.84D(7岁)、-0.29±1.41D(8岁)、-0.18±1.35D(9岁)。10~13岁组学生2018~2020年近视患病率及SE基本保持稳定(P>0.05)。结论:新冠疫情居家隔离期后,6~9岁学生的近视进展明显加快,应更加重视6~9岁近视防控的窗口期。     

上海市青浦区小学生近视的调查分析

目的:调查上海郊区近视眼的流行病学状况,并研究近视眼的发病率与地区、性别、年级的关系。方法:用随机整体抽样的方法在上海青浦区抽取3所小学,调查3517例小学生,托吡卡胺散瞳后进行验光,静态屈光>-0.50D定义为近视,并用SAS6.12软件进行统计。结果:青浦区小学生近视眼患病率为14.53%。城镇学生的近视患病率高于欠发达地区。女生的近视患病率(16.08%)比男生(13.30%)高。随着年级增高,近视患病率也逐渐增高。结论:青浦地区小学生的近视率较高,近视发病率与地区、性别、年级均相关。     

湖北省荆州市沙市区中小学生近视现况调查及影响因素分析

目的:调查2017年荆州市沙市中心区和城乡区中小学生近视患病率及影响近视发生的因素,为近视防控提供科学依据。方法:采用整群分层抽样方法,选择沙市中心城区和城乡结合区学校7~18岁中小学生10353名,近视人数5456人,患病率52.70%。采用问卷调查的方式收集现场调查问卷共计10353份,进行相关因素Logistic回归分析。结果:本次调查研究对象为沙市中心城区的8所中小学和城乡结合区6所中小学,沙市中心城区的近视患病率为60.34%,城乡结合区的近视患病率为11.43%(P<0.01)。户外活动和正确的读写姿势是近视的保护因素,而年龄、使用电子产品时间、课外连续作业时间是近视的危险因素。结论:荆州市沙市区的中小学生的近视率已处在较高的水平,尤其是中心城区中小学生的近视率,学校、家庭应共同努力,增加青少年户外活动时间,改善青少年用眼环境,预防及减缓青少年近视的发生发展。     

中山市2006～2007年中小学生近视调查分析

目的 探讨中山市中小学近视情况及相关因素.方法 采用随机整群抽样调查方法.在2006年至2007年期间,对中山市中小学通过随机抽样在市区和镇区6所学校(包括市区3所镇区3所)进行调查,采用问卷调查和散瞳验光检查其屈光度.各年级间及镇区与市区之间学生近视发病率采用卡方检验,近视率与用眼时间用相关系数分析.结果 此次调查对象共9379人,近视5443人,近视率58.03%,近视率从小学一年级8.04%上升到高三86.68%,市区和镇区小学近视率差异无统计学意义(P＞0.05),初中阶段市区近视率明显高于镇区(P＜0.01),高中阶段高三毕业班近视率明显高于高一高二非毕业班(P＜0.05镇区P＜0.001市区).此次调查中眼保健操对预防近视加深无明显作用(P0.05),每天看书总时间、一次持续看书时间、看课外书时间与近视发生呈正相关,相关系数分别为0.995、0.992、0.999.结论 中山市中小学生近视率较高,近视率与用眼时间密切相关.如何适当减轻学生的学习负担是预防近视的关键.