Prevalence of cataract and cataract surgery in urban and rural Chinese populations over 50 years old: a systematic review and Meta-analysis

INTRODUCTION

C ataract was one of the main causes of blindness which remained a major public health problem worldwide.The prevalence of cataract in developing countries was higher and the age of onset was earlier, Asia contributed the majority particularly. In China, cataract was the leading cause of low vision and blindness. Cataract were the primary causes of visual impairment in adults over 60 years old, despite the continuous efforts of public health to improve the cataract surgery rate. In terms of economic burden, most countries faced serious economic burden and global health progress in cataract was accompanied by widening inequality, with cataract burden being more concentrated in countries with lower socioeconomic status. China also endured a huge economic burden based on the number of patients. This made the cost of medical treatment and social impact caused by cataract blindness lead to serious damage to the economy all over the world. Although cataract was not fatal, it still had a negative influence on the quality of life in cataract patients.The most common cause of cataract was the denaturation of protein which led to the opacity in lens. It was commonly observed in people over 50 years old, and the morbidity increases with age. Its occurrence was linked to the degeneration of metabolism in the elderly. So cataract had a profound impact on the quality of life of the elderly in pace with age. Figuring out a way to investigate the prevalence of cataract and further guide cataract screening to improve the quality of life will be one of the urgent challenges which China needs to face. Since the 1990s, Chinese researchers had started to survey and analyze the prevalence of cataract in many areas, and the results explained that cataract was still the main cause of blindness. With the increasing proportion of the elderly in the population, the number of cataract patients in China would increase year by year, and the increasingeconomic burden caused by cataract was an inevitable problem. The prevalence of cataract and cataract surgical coverage has significant disparities among different regions and nationalities. However, the research on the prevalence and cataract surgical coverage in China has not been integrally analysed, which also limited the extensive cataract screening and popularization of cataract surgery in the future.In order to further analyses the prevalence of cataract and reduce the economic burden, it was necessary to investigate the epidemiology of cataract. The purpose of this study was to summarize and analyses the research on the prevalence of cataract in China, expecting to get a preliminary assessment of the prevalent trend and provide a theoretical evidence for further cataract screening.

SUBJECTS AND METHODS

Cataract surgical coverage represents the coverage of cataract surgery among cataract patients. Ⅰt reflects the popularity of cataract surgery in study area, but do not distinguish the types of surgery and regions in this Meta-analysis. The results showed that the median of cataract surgical coverage in China was 7.18%, the lowest was 3.47%, and the highest was 17.69%. Heterogeneity test showed that there was statistical difference between the included studies (=97.1%,<0.01). Meta-analysis after using random effect model showed that the cataract surgical coverage in China was 9.19% (95%CI: 7.16%-11.22%). Forest map was shown in Figure 11.

The literature was collected and screened by Endnote X9, then the related literature was screened according to the inclusion and exclusion criteria. After that, titles and abstracts of the remaining studies would be independently scanned by three authors (Du YF, Liu HR and Zhang Y). In this step, literature was selected subjectively in order to judge whether it is related to this Meta-analysis. These selected literatures would be compared, and inconsistent problems were solved through negotiation. Then we read the full text of the remaining studies to determine whether they met our inclusion criteria,but studies that were not available for the full text would be excluded. Finally, according to Chinese urban and rural classification standards (Chinese administrative divisions, the scale of county and above was urban, and the scale of village and township was rural), the literature was divided into urban and rural categories.

In this study, the data were extracted on the basis of prescribed process, which the details were shown in Table 2. Quality assessment was based on the quality assessment criteria proposed by Khambalia and Seen, and the results of quality score were as follows: 2 papers scored 1, 7 papers scored 2,9 papers scored 3, 1 paper scored 4, and 1 papers scored 5(Figure 3).

The inclusion criteria were as follows:1) The purpose of these literature was to investigate the prevalence of cataract in China, and the cases included were consecutive; 2) The sampling method should be random sampling, and subjects were healthy people in a stationary region; 3) The subjects were aged 50 or above, and were stratified according to different age groups; 4) The diagnosis method of cataract was reasonable and met the standard(Figure 1); 5) The prevalence of cataract can be directly extracted or can be calculated from the original data.

The exclusion criteria were as follows:1) Research method was cohort study, or the study type was “comments”, “l(fā)etter”, “review”, “case report”,; 2)Repetitive articles or duplicate studied population from the identical area; 3) Had tendency when select the studied population; 4) Research data were incomplete.

We extracted the basic data of the final qualified literature, including the author, publish year, study region, regional category, age, sample size, literature quality score,. And research data were extracted from the literature include the number of samples older than 50y, the number of cataract patients and the prevalence.

The quality of included studies was evaluated using the quality assessment criteria of literature proposed by Khambalia and Seen. Then the included literature was scored and summarized according to these criteria (Table 1).

Other data: We also collected and collated the other data of some literature in this Meta-analysis, including the prevalence of cataract in urban and rural areas respectively, the prevalence of cataract in different age groups, and the cataract surgical coverage.

開展教學(xué)活動的前提是系統(tǒng)地研究學(xué)生的學(xué)情。學(xué)情分析是系統(tǒng)工程，既要了解學(xué)生學(xué)習(xí)的起點狀態(tài)，又要研究學(xué)生的潛在狀態(tài)。學(xué)生的學(xué)習(xí)起點狀態(tài)包括學(xué)生的認(rèn)知基礎(chǔ)、學(xué)習(xí)能力、學(xué)習(xí)態(tài)度、學(xué)習(xí)習(xí)慣、意志品質(zhì)等。學(xué)生的潛在狀態(tài)指學(xué)生可能發(fā)生的狀況與可能的發(fā)展，主要說明學(xué)生在知識與技能，過程與方法，情感、態(tài)度與價值觀方面都能參與到什么程度，達(dá)到什么狀態(tài)等。

第一代路虎發(fā)現(xiàn)僅擁有三門版一種車身形式，但幾乎所有人都明白在不久的將來，它會得到空間靈活度更高，駕乘體驗更為優(yōu)秀的五門版車型。

Cataract was one of the main causes of blindness in the world,which accounts for about half of the entire blind people.But the prevalence of cataract in China varies markedly due to regional distribution and examination methods. Metaanalysis was still developing in the world for a short time,when there were not enough time or funds to do a national survey, we can make a Meta-analysis of the results from the existing local epidemiologic surveys to increase the sample size and the diagnostic efficiency, make the research results have statistically significant. This Meta-analysis showed that the pooled prevalence of cataract in China was 27.45%(95%CI: 24.38%-30.52%), which was similar to the results of most previous epidemiological studies in the world. And with the increase of age, the prevalence of cataract increased significantly. Based on the large number of cataract patients in China, the cataract surgical coverage still has room for improvement compared with many countries and regions(Table 3).

RESULTS

Totally 20 studies were finally included for Meta-analysis through literature screening.The detailed screening process was shown in Figure 2. The total number of participants in all studies contained in this Meta-analysis was 111 434, and 31 551 were cataract patients.Among these studies, the minimum sample size was 279, and the maximum sample size was 20 860, of which the median was 5010, and the interquartile range was 2413-5300. The epidemiological investigations involved in these studies were distributed in the urban and rural areas of 15 provinces or cities, including Beijing, Zhejiang, Guangdong, Hainan, Hebei,Heilongjiang, Jiangsu, Jiangxi, Ningxia, Shandong, Shanghai,Sichuan, Tianjin, Yunnan, and Chongqing. The median prevalence of cataract was 28.81%, the lowest was 15.57%, the highest was 39.86%, and the interquartile range was 21.96%-32.77%.

轉(zhuǎn)錄因子在異戊二烯代謝生物合成中起著重要作用，這些因子結(jié)合特殊結(jié)構(gòu)基因功能，調(diào)控相關(guān)基因的協(xié)同表達(dá)，刺激或抑制異戊二烯化合物的積累.本研究找到了多個與異戊二烯代謝類物質(zhì)代謝有關(guān)的轉(zhuǎn)錄因子，為借助細(xì)胞懸浮培養(yǎng)技術(shù)生產(chǎn)青錢柳三萜類、多糖與戊烯苷等生物活性成分，并通過調(diào)控次生代謝相關(guān)基因表達(dá)獲得較高的產(chǎn)量提供了參考.

Heterogeneity analysis showed that the prevalence of cataract was statistical heterogeneity among these studies(=99.2%,<0.01), so the random effect model was used in Meta-analysis. The results showed that the prevalence of cataract over 50 years old in China was 27.45% (95%CI:24.38%-30.52%). Forest map was shown in Figure 4.

The median prevalence of cataract was 28.97%in rural areas, and the lowest was 22.40%, the highest was 34.95%. Heterogeneity test showed that there was statistical difference between the included studies (=97.8%,<0.01),so the random effect model was used for Meta‐analysis. The results showed that the prevalence of cataract in rural areas was 28.79% (95%CI: 25.45%-32.12%). The median prevalence of cataract was 26.17% in urban areas, and the lowest was 15.57%, the highest was 35.76%. Heterogeneity test showed that there were statistical differences among these studies(=99.4%,<0.01). Meta-analysis showed that the prevalence of cataract in urban areas was 26.66% (95%CI: 21.99%-31.34%). Forest maps were shown in Figures 5 and 6.

The prevalence of cataract in different age groups was statistically analysed base on the length of 10y. Results showed that the median prevalence of cataract in 50-59 age group was 5.23%,the lowest prevalence was 2.39%, and the highest prevalence was 16.81%. The heterogeneity test showed that there was statistical difference between the included studies (=98.8%,<0.01). Meta-analysis using random effect model showed that the prevalence of cataract in the age group of 50-59y was 7.88% (95%CI: 5.59%-10.18%). The median prevalence of cataract in 60-69 age group was 25.37%, the lowest was 10.90%, and the highest was 42.14%. Heterogeneity test showed that there was statistical difference between the included studies (=99.1%,<0.01). So Meta-analysis showed that the prevalence of cataract was 24.94% (95%CI:20.28%-29.60%). The median prevalence of cataract in 70-79 age group was 50.72%, the lowest was 41.47%, and the highest was 69.44%. Heterogeneity test showed that there was statistical difference between the included studies (=97.4%,<0.01). Meta-analysis showed that the prevalence of cataract in 70-79 years old was 51.74% (95%CI: 45.75%-57.72%).The median prevalence of cataract over 80 years old was 82.42%, the lowest was 64.84%, and the highest was 85.71%.Heterogeneity test showed that there was statistical difference between the included studies (=87.3%,<0.01). So Metaanalysis showed that the prevalence of cataract over 80 years old was 78.43% (95%CI: 74.02%-82.83%). Forest maps were shown in Figures 7-10.

We searched PubMed, EMBASE, Web of Science, Wanfang Data, and CNKI for literature about the prevalence of cataract in China. In order to cover comprehensive related literature as much as possible, the search terms were set as“cataract” or “cataracts” and “prevalence” or “epidemiology” or“incidence” and “China” or “Chinese”. The time of publication was limited from July 2000 to July 2020, and the language of publication was English.

當(dāng)然，換在以前，穿幫的只是公開發(fā)表的文稿，而那些數(shù)量更多的內(nèi)部使用或僅用于存檔備查的文案，則幾乎無人關(guān)注，即使偶爾露出馬腳，人們也只是一笑了之，后果嚴(yán)重不到哪里去。也正是因為如此，偷懶的人繼續(xù)偷懶，偷文的人照偷不誤，各類奇葩新聞時時曝光，為豐富多彩的生活平添若干生動素材。

The publication bias of this study was analysed by Eggers’ test. Results of Eggers’ test showed that=-0.22,=0.826,>0.05, so there was no significant publication bias. Funnel plot of publication bias was shown in Figure 12.

第二種方案，將基帶矩陣作為整個傳輸系統(tǒng)的核心，周邊配置IP和SDI的轉(zhuǎn)換設(shè)備來實現(xiàn)兩種信號之間的轉(zhuǎn)換。這種接入方式初 期較容易，但隨著IP信號越來越多的接入，會大量增加IP和SDI的轉(zhuǎn)換設(shè)備，當(dāng)系統(tǒng)內(nèi)大多數(shù)設(shè)備都支持IP接口時，就要面臨將矩陣更換為交換機(IP矩陣)，之前大量購置的IP和SDI的轉(zhuǎn)換設(shè)備將被淘汰。此方案入門容易但后續(xù)工作較復(fù)雜。

DISCUSSION

Meta-analysis was performed by Stata v15SE (StataCorp, College Station, TX, USA) in this study.According to the prevalence of cataract in these literatures, thepooled prevalence of cataract in Chinese population over 50 years old was calculated. Subgroup analysis was conducted according to the types of regions, different age groups and cataract surgical coverage. Effect size (ES, the ratios in all eligible studies were combined, which called pooled ratio)with 95%CI was evaluated and the forest map was drawn according to the results. And the homogeneity test was also used, which setto quantitatively determine the level of heterogeneity when=0.1. The included studies were considered to be homogeneous when≥0.10 and≤50%,and the fixed effect model was selected for Meta-analysis;On the contrary, if<0.1 and>50%, it is considered that there was heterogeneity among the included studies, and the random effect model (REM, a generalization of the classical linear model) was selected for Meta-analysis. While the publication bias was analysed by Eggers’ test.

The results from this study showed that the prevalence of cataract was 26.66% (95%CI: 21.99%-31.34%) in urban areas and 28.79% (95%CI: 25.45%-32.12%) in rural areas. The prevalence of cataract in rural areas is higher than that in urban areas. Due to the difference of economy and education between rural and urban areas, the awareness of disease and the desirability of treatment are relatively low in rural areas. This suggests that cataract screening to popularize the knowledge of cataract and the latest research progress are an effective method to reduce the prevalence of cataract in rural areas, and carry out cataract surgery camps in the local area could be a safe and effective way to reduce cataract cases. Compared with the prevalence of cataract in other countries all over the world, we found that the prevalence of cataract in China stayed at an intermediate level (over 60 years old). But the prevalence of cataract was still nearly 40%, together with Chinese population, these would easily make China become one of the countries with heavy burden of visual impairment by cataract in the world, which should arouse our attention.So comprehensive screening of cataract and popularization of cataract knowledge is one of the necessary measures. The specific results of other countries in the world were shown in Table 4.

The prevalence of cataract varies evidently among different age groups. The results of this study show that the prevalence of cataract in the age group of 50-59 years old is 7.88%, the prevalence of cataract in the age group of 60-69 years old is 24.94%, and the prevalence of cataract in the age group of 70-79 years old has increased to 51.74%, while the prevalence of cataract in more than 80 years old is 78.43%. This can be found that with the increase of age, the prevalence of cataract also showed a significant growth trend. The increase of age can lead to the decline of metabolic capacity in lens, and eventually lead to the occurrence of cataract, which was the main cause of cataract. Cataract usually begins to occur at the age of 40, but most of them are over 50 years old when slit lamp examination can detect or cause visual impairment.Therefore, it also indicates that the prevalence of cataract increases rapidly after 50 years old, and with the accumulation of cases, the prevalence of cataract in each age group increases significantly. But with the accumulation of systemic diseases,some risks would be brought for the elderly cataract patients to choose surgical treatment, and the growth of age will bring other eye diseases, even the choice of cataract surgery may not be able to achieve satisfactory results. So, the recognition and timely selection of surgical treatment are the first choice to ensure the vision and quality of life.

從建筑、工業(yè)、旅行、時尚，到汽車、摩托車、食物、杯具，和我認(rèn)識的許多設(shè)計師不同，吳濱的喜好目錄真的可以說上三天三夜。而在眾多喜好之中，吳濱和我一樣都對英國車有著強烈的好感。

Phacoemulsification combined with intraocular lens implantation was one of the most effective surgical methods for cataract, but the cost of surgery and intraocular lens was still difficult for part of the population to afford. The outcomes of this Meta-analysis show that the cataract surgical coverage in China is 9.19% (95%CI: 7.16%-11.22%). Although the popularity of cataract surgery in some economically developed areas has been relatively high, which even can reach the level of developed countries. But there is still room to improve the cataract surgical coverage in China. Economic burden may be one of the main factors that affect the treatment of cataract.In addition, lack of the concept of cataract and the backward way of thinking still restrict the selection of treatment for some people with poor education. Due to the lack of concrete classification in this study, the Meta‐analysis cannot be carried out in terms of operation rate. However, we speculate that the operation rate of cataract in rural areas will be less than that in urban areas due to the above reasons. Jongsareejithave found that small incision cataract surgery was a more effective surgical method than cataract phacoemulsification. And the improvement of the medical treatment level has gradually simplified the implementation of cataract surgery, which could relieve the economic burden of cataract blindness.

There are still some limitations in this study: 1) The existence of heterogeneity is one of the main reasons to limit the credibility of the results. We believe that this heterogeneity is mainly due to different regions, ethnic minority, diagnostic criteria and other factors, but the concrete factors that may affect the prevalence of cataract need further research;2) Although this study has covered most areas of China comprehensively, it still cannot fully reflect the prevalence of cataract in all regions of China; 3) The epidemiological investigation involved in this study has a fixed period of time(2000-2020), and the prevalence of cataract could change with time which will inevitably affect the results; 4) Due to the difference of examination instrument in many regions, the diagnosis and definition of cataract may be different, which also leads to the bias of the prevalence; 5) Other factors such as publication bias (published articles tend to have significant positive results), selection bias (the process of screening articles and the population involved in the epidemiological survey) will also affect the results of this study.

In conclusion, this Meta-analysis showed that the prevalence of cataract in China was still at a high level, due to the lack of awareness of cataract and cataract surgery, the promotion of cataract surgery still needs to be further improved, and the decline of quality of life caused by cataract is worthy of attention. So, it’s obviously that the opportunistic treatment to find cataract was not enough. Cataract blindness and severe visual impairment have become serious public health problems. Therefore, health institutions should play the leading role to integrate social resources, and implement intervention on cataract blindness and severe visual impairment through regular screening of cataract. And cataract surgery rate may be increased by involving non-government organizations(NGO). We should propaganda the knowledge of cataract and develop more cataract surgical training, so as to solve the economic burden caused by cataract.

政府和社會一直大力支持和倡導(dǎo)“全民閱讀”，為了鼓勵民眾培養(yǎng)良好的閱讀習(xí)慣， 2017年在國務(wù)院法制辦會議審議并原則通過《全民閱讀促進條例（草案）》中，計劃將全民閱讀納入國家戰(zhàn)略。[1]全民閱讀已成為全社會共同參與的一項重大工程，以大學(xué)生為目標(biāo)群體的高校圖書館在全民閱讀中有著不可推卸的責(zé)任，承擔(dān)著重要的角色。從20世紀(jì)90年代末至今，高校圖書館服務(wù)內(nèi)容在不斷發(fā)生變化，閱讀推廣作為新興服務(wù)門類，發(fā)揮著越來越重要的作用，包括讀書講座、閱讀研討、展覽、影視鑒賞等內(nèi)容的閱讀推廣活動成為圖書館評估工作中的重要一環(huán)。許多高校圖書館成立專門的閱讀推廣部門，組織專業(yè)的閱讀推廣團隊策劃組織閱讀活動。

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