Research on the Development Status and Trends of Glaucoma Study Based on SCIE for Ten years

Background To explore the development status and trends of glaucoma study from 2009 to 2018 based on SCIE. Methods Searching for glaucoma-related articles published in SCIE in the last decade and describing the distribution of the time, region, author, author institution, journal and inuence of articles. Meanwhile, we compared the publication of articles, the research hotspots among ve years before and after 2009-2013, 2014-2018. Results A total of 19,609 glaucoma-related articles were retrieved during 2009-2018 and the global SCIE articles have increased year by year from 2009 to 2017. The top ve countries for articles were the United States, China, Japan, Germany and the England. The top three authors are Weinreb, R N, Aung, T and Jonas, J B. The journal with the largest number of published articles is INVESTIGATIVE OPHTHALMOLOGY VISUAL SCIENCE. It can be seen that glaucoma-related pathogenesis research, OCT and other imaging examinations in the diagnosis and treatment of glaucoma and glaucoma surgery have attracted much attention. Conclusions In the past ten years, global glaucoma research has developed in a balanced manner, and the cooperation between various institutions and teams has become increasingly close. The research hotspots are still concentrated in the pathogenesis and diagnosis and treatment of glaucoma. affected in 2020 and 2040. The study concludes that global prevalence rate of glaucoma in 40–80-year-old people is 3.54%. Highest POAG prevalence is in Africa. Highest PACG prevalence is in Asia. In 2040, the number of glaucoma patients worldwide will increase to 111.8 million. The study is important for the design of glaucoma screening, treatment and related public health strategies. research has developed in a balanced manner, and the cooperation between various institutions and teams has become increasingly close. The research hotspots are still concentrated in the pathogenesis and diagnosis and treatment of glaucoma. This study is based on the analysis of large sample bases and has important reference value for revealing the macroscopic situation in the glaucoma research eld. We believe that strengthening international exchanges and cooperation will be an important way to advance scientic research in the eld of glaucoma.


Background
Glaucoma is the leading cause of irreversible blindness in the world. Because of its high prevalence rate, high blindness rate and irreversible damage, it has become a major public health problem in China and the world. Searching and analyzing the related publications of glaucoma can comprehensively and intuitively understand the current research status and research hotspots, which plays an important role in the optimization of glaucoma research and clinical work.
This paper searches and analyzes the relevant literature data of glaucoma for the past ten years (2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)  The top 10 countries are listed in Table 2, the top three countries are the United States, China and Japan, which respectively accounted for 32.439%, 11.882% and 7.716% of the total number of articles in the past 10 years.
Author's co-occurrence gure The mean of co-occurrence matrices analyzed the top 50 authors in the number of articles. On this basis, the author's co-occurrence map was constructed and shown in Figure 1. This visualizes the author's clustering results and re ects the cooperation between the authors to some extent. The larger the circle in the gure, the larger the number of articles published by the author. Thicker the lines, more cooperation between authors. Due to the complicated cooperation between the authors, we increase the visual effect of the co-author map by setting the edge value of the map display to 12 (That is, the connection will be displayed only when the number of the author's cooperative publication is no less than 12).

Distribution of authors
Use SCI regulatory institution name and take the top 20 ins institutions. The top 3 institutions are the UNIVERSITY OF CALIFORNIA SYSTEM, UNIVERSITY OF LONDON and UNIVERSITY COLLEGE LONDON Author's institution (organization) co-occurrence map For the imported TDA data, we use " the Author A liations (Organization Only) " eld, after the data cleaning, to take the top 50 institutions (organization only) to build a co-occurrence matrix, which visualizes the results of the author's institutions clustering and re ects the cooperation between institutions to some extent. The larger the circle in the gure, the larger the number of articles published by the organization. The thicker the lines, the higher the cooperation frequency between the organizations. Due to the complicated inter-institutional cooperation, we increase the visual effect of the co-occurrence map by setting the edge value to 20 (That is, the line will be only displayed when cooperation article numbers are no less than 20).

Distribution of keywords
Based on the keyword (author's'), after the data is cleaned and processed, the keywords appeared in more than 100 articles are obtained and shown in Table   9. The top three keywords are glaucoma, intraocular pressure and OCT.

Keywords co-occurrence map
Build the co-occurrence matrix by the top 50 keywords, on the basis of which we make a co-occurrence map. So, we can visualize the clustering results. The larger the circle in the gure, the larger the number of the article. The thicker the line, and the stronger the correlation between keywords. The keywords of the cross line can be seen as discussion hotspots (i.e. all the keywords given in the gure). Since the co-occurrence relationship between keywords is complicated, we increase the visual effect of the co-occurrence map by setting the edge value of the map to 5 (That is, the inter-keyword connection will be displayed only when they appeared simultaneously in no less than 5 articles).

Discussion
Discussion of publication status and regularities of distribution of glaucoma articles in the past decade The United States, China, and Japan have become the top three countries in the number of articles, leading the development of intercountry glaucoma research. This article focuses on the authors who have published the most articles in the top ten countries and the most cited articles, aiming to explore the teams leading the development of glaucoma research, their outstanding contributions and their primary research areas, providing direction for intercountry cooperation. Professor Weinreb RN from the United States is the rst, who has published a total of 325 articles in the past 10 years. The most cited article is Retinal Nerve Fiber Layer Imaging with Spectral-Domain Optical Coherence Tomography A Variability and Diagnostic Performance Study [1] , which is quoted as high as 276 times. Professor Weinreb RN notes that spectral-domain OCT shows less variability than time-domain OCT in the measurement of the retinal nerve ber layer in this article, which suggests the spectral-domain OCT is in more meaningful in assessment of glaucoma progression (by measuring the optic nerve ber layer thickness).It guides the application of OCT in the assessment of glaucoma progression is with an important clinical signi cance.
Japanese professor ARAIE M has published 117 articles in the past 10 years. The most cited one is Effects of Age, Sex, and Axial Length on the Three-Dimensional Pro le of Normal Macular Layer Structures [2] , cited 107 times. In this paper, professor ARAIE M points out that the structure of normal macular area is related to age, gender and axial length, suggesting that these factors need to be considered when using the spectral-domain OCT to study the structure of the macular area on patients with retinopathy and glaucoma. It guides the clinical application of OCT and accurate structural measurement. The sixth article from Korean professor team of Eun Ji Lee applies depth imaging technique-spectral domain OCT and the whole thickness of the lamina cribrosa can be clearly visualized. This technology can promote the study of lamina cribrosa in glaucoma patients, and also provide a method for studying the mechanism of optic neuropathy. The seventh article from Indian professor RAO HL nds that the use of RTVueOCT to measure retinal nerve ber layer and retinal macular thickness can signi cantly better detect glaucoma visual eld defects than the papilla of the optic nerve. These four heavyweight articles thus con rm countries follow the application of OCT in the diagnosis and treatment of glaucoma and glaucoma pathogenesis.
Professor Wang Ningli from China has published 136 articles in the past 10 years. The most cited article is Cerebrospinal Fluid Pressure in Glaucoma A Prospective Study [3] , which has been cited for up to 232 times. Professor Wang Ningli rstly discovers that the intracranial pressure of normal-tension glaucoma patient is low and the pressure difference across the lamina cribrosa is high through prospective study, suggesting that the two factors of intraocular pressure and intracranial pressure should be considered in the diagnosis and treatment of glaucoma. The treatment should aim at balancing the pressure gradient of the eye, and the study established the theory of optic nerve damage caused by inadequate pressure gradient of the eye for the rst time in the world, which is a milestone.
In epidemiological studies, Professor JONAS JB collects the cause of vision loss in the globe during 1990-2010 [4] . In 2010, the world had 65% of blind patients, and 76% of moderate to severe visual impairment patients may have a cause that can be prevented or treated. The causes of blindness vary among patients in different regions, but women worldwide are more likely than men to have blind or moderate to severe visual impairment due to cataracts and macular degeneration. In order to guide public health policy, systematic analysis of the proportion of causes have been ongoing in the past few years, which has a guiding signi cance for the resource allocation of ophthalmic disease control. The fth Singapore -India -China cohort study compares the incidence, risk factors and effects of major ophthalmic diseases among Chinese and Indian Malaysian ethnic groups [5] . The study helps to understand the different environmental and genetic impacts of different ethnic groups. In addition, although not in the top ten countries, the Singapore Institute of Ophthalmology published a META study Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and metaanalysis [6] , the most cited article in the past decade. This paper systematically analyzes 50 studies data of population-based studies and predicts the number of affected in 2020 and 2040. The study concludes that global prevalence rate of glaucoma in 40-80-year-old people is 3.54%. Highest POAG prevalence is in Africa. Highest PACG prevalence is in Asia. In 2040, the number of glaucoma patients worldwide will increase to 111.8 million. The study is important for the design of glaucoma screening, treatment and related public health strategies.
The ninth and tenth study from Turkish and Italian respectively are related to drug treatment. One proposes that in exfoliation glaucoma, whether the administration is in morning or evening, the group of a xed combination of bimatoprost and timolol can control 24 hours intraocular pressure better than any group of a single medicine [7] . Another suggests that dithiocarbamates can inhibit carbonic anhydrase activity and exhibit an effect of effectively reducing intraocular pressure in vivo. This new carbonic anhydrase inhibitor provides a new drug candidate for anti-glaucoma drugs [8] .
The authors and articles of the above ten countries represent the development of direction of epidemiology, diagnosis and treatment of glaucoma in the past decade. In addition, the top 3 countries that have most articles published are the United States, China and Japan, which accounted for nearly 32.439%, 11.882% and 7.716% of the total number of articles respectively. In the ve years before and after the comparison, it can be seen that the number of articles from the United States has declined in the past ve years, and the number of articles in several Asian countries has increased signi cantly, such as China, South Korea, Japan, and India. Among the top 20 authors, the number of authors from Europe and America and authors from Asia is 1:1. And the development in all regions of the world is comparable. Exchanges and cooperation between agencies can promote the progress of science. Before and after the comparison, the frequency of cooperation among authors in the core author group has increased in the past ve years, and the frequency of cooperation between Asian countries and Western countries has also increased signi cantly.
The distribution of fund agencies can show that the authority maintains a leading position: Research to Prevent Blindness (RPB), National Institutes of Health (NIH), National Natural Science Foundation of China, and the National Natural Science Foundation of China has increased its funding for the past ve years, leaps to rst in the ranking. In the past ve years, the number of Japanese funded articles has increased signi cantly. The agencies are the Japan Ministry of Education, Culture, Sports and Science, Santen, Japan, and the Japan Society for Promotion Science.

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The keyword is the most accurate and concise disclosure of the content of the article. It re ects the main research content of the paper to a large extent and implies the research status, hotspots and development laws of the subject. Based on the author's keywords, this paper performs statistics after data cleaning and takes the keywords appeared in more than 100 articles, as shown in Table 9. The top three keywords are glaucoma, intraocular pressure and OCT. Build the co-occurrence matrix by the top 50 keywords, on the basis of which we make a co-occurrence map. So, we can visualize the clustering results.
The larger the circle in the gure, the larger the number of the article. The thicker the line, and the stronger the correlation between keywords. The keywords of the cross line can be seen as discussion hotspots. It can be seen from Figure 3  This research belongs to the exploratory research based on published literature, and it has certain limitations. Based on the frequency of keyword occurrence, the research hotspots may miss the latest hotspots. However, it basically conforms to the development law of the international glaucoma eld in the past ten years.

Conclusion
In the past ten years, global glaucoma research has developed in a balanced manner, and the cooperation between various institutions and teams has become increasingly close. The research hotspots are still concentrated in the pathogenesis and diagnosis and treatment of glaucoma. This study is based on the analysis of large sample bases and has important reference value for revealing the macroscopic situation in the glaucoma research eld. We believe that strengthening international exchanges and cooperation will be an important way to advance scienti c research in the eld of glaucoma.