Visualized analysis of research on myopic traction maculopathy based on CiteSpace

Heng-Di Zhang, Ling Zhang, Fei Han, Ning Lin, Wei Jiang

1Department of Ophthalmology, the General Hospital of Western Theater Command, PLA, Chengdu 610083, Sichuan Province, China

2Department of Oncology, the General Hospital of Western Theater Command, PLA, Chengdu 610083, Sichuan Province,China

3Department of Clinical Nutrition, the General Hospital of Western Theater Command, PLA, Chengdu 610083, Sichuan Province, China

Abstract

● KEYWORDS: myopic traction maculopathy; bibliometric analysis; CiteSpace

INTRODUCTION

Myopic traction maculopathy (MTM) refers to a spectrum of sight threatening diseases including retinoschisis/maculoschisis/foveoschisis, foveal/retinal detachment, lamellar macular holes and full-thickness macular holes with or without retinal detachment (MHRD)[1].MTM is a major cause of blindness in pathologic myopia (PM).Up to 35% of pathologic myopes were reported to be affected by MTM[2].Considering the threat of MTM and PM to public health (7% of the Western population and 12%-27% of the Asian population suffered from visual disability caused by PM)[3], it is important to understand MTM and its associations.Various studies have been published in this area, such as surgical approaches aiming at resolving tangential and perpendicular traction force, as well as new classifications based on emerging detection technology, but controversy and uncertainties still remain.Therefore, visual analysis research of this field is valuable in providing an overview and generating a more comprehensive understanding of MTM research about the achievements and future research trends.CiteSpace is a widely used software which provides insights into research areasviaanalyzing co-cited references, co-occurrence keywords and other information based on bibliographic records from the Web of Science (WOS).In this study, we aimed at investigating scientific hotspots, research trends, and frontiers in MTM research based on CiteSpace from the WOS database.

MATERIALS AND METHODS

Data AcquisitionData were collected for bibliometric and visualization analyses from WOS Core Collection.We used“myopic traction maculopathy”, “myopic macular schisis”,“myopic retinoschsis”, and “myopic macular hole” as the search terms to retrieve MTM-related studies.Articles published between 2005 to 2022 were retrieved.Document types were restricted to articles and reviews, without language or data category restrictions.After removing irrelevant and duplicate documents using CiteSpace, a total of 839 related studies were retrieved finally.

Research MethodsExported records were analyzed for titles, publication years, research institutions, journal names,authors, keywords and abstracts.Data were downloaded from WOS and 500 pieces of data as one file were imported into CiteSpace software version 6.1 one by one for quantitative and qualitative analyses.

Parameter SettingsTime-slicing was set between 2005 and 2022 (1y per slice).The co-occurrence of keywords and co-cited reference were selected to generate a visualized knowledge network for analysis.The threshold (top N per slice) was set to 50, and the critical path (Pathfinder) and pruning graph (Pruning Sliced Networks) were selected as the pruning options.Nodes and links were used to generate visualization knowledge graphs.Each node in the graph represented an element to be analyzed, such as a cited journal, an institution or an author.Different colors of the node correspond to different years, and the size of the node represented the frequency of the citation.The links between nodes represented the co-occurrence or co-citation relationship.The thickness of the linking lines represented the strength of the relationship, and the color corresponded to the first cocitation or co-occurrence time of nodes.Cool colors indicate earlier years and warm colors indicate more recent years.Nodes with high betweenness centrality (＞0.1, node presented with purple rings on the outer circle) were usually considered turning points or pivotal points in a field.

RESULTS

Articles Published in MTM-Related ResearchAltogether 903 MTM-related publications were retrieved.After preprocessed by CiteSpace software, 64 literature records unrelated to the subject were excluded, and 839 articles were finally included, among which 734 were articles and 105 were reviews.The annual number of publications increased from 1 in 2005 to 106 in 2022.The average annual number of published articles was 46 (Figure 1).

Analysis of Journals and Co-Cited JournalsThe 159 journals were involved in MTM-related research area after statistical analysis, from which the top five journals were screened out.The highest impact factor of the related journal was 36.61 while the average impact factor was 3.68,suggesting that MTM research was a highly topical subject area.Research results for MTM were mainly distributed in the‘Ophthalmology’ and ‘Medicine general internal’ areas.Cocited journals were those cited together by other researchers,and co-citation analysis indicated the distribution of key knowledge sources in the MTM research field.The most frequently cited journal wasAmerican Journal of Ophthalmology,followed byOphthalmology, whileBiomaterialranks the first in terms of centrality.

Figure 1 The number of myopic traction maculopathy research publications from 2005 to 2022.

Figure 2 A country/region cooperation map related to myopic traction maculopathy research from 2005 to 2022 The nodes in the map represent countries/regions.The lines between the nodes represent cooperation relations.

Analysis of Countries/RegionsThe countries/regions cooperation network map is shown in Figure 2.Node number and size correspond to the publications volume generated by countries/regions, and the thickness of connective lines between nodes indicated the strength of cooperation between them.MTM research outputs were mainly derived from different regions of Asia, the Americas, and Europe, which is consistent with the high morbidity of PM in these regions.Altogether 839 references were published by research groups in 52 countries, and the top five countries/regions were China,the United States, Japan, Italy, and Germany.The top five countries/regions in terms of centrality were the United States(0.40), England (0.38), Australia (0.16), Italy (0.12), and Germany (0.12).The centrality of these five countries was greater than 0.1, indicating that these countries had a certain influence in the field of MTM research.The network density was 0.1131, suggesting a weak to moderate cooperative strength between countries/regions.

Analysis of InstitutionsSeveral research institutions contributed to the study outputs of MTM, among which the Tokyo Medical and Dental University ranked first with 47 articles, followed by the Capital Medical University and Sun Yat-sen University.The top 10 institutions published 31.59% of MTM studies.

Figure 3 Timeline view of myopic traction maculopathy research hotspots.

The network density in this study was 0.0073 (＞0.5 denotes a tight network), which indicated that the global MTM research cooperation network was relatively weak.The Singapore Natl Eye Center displayed a good domestic cooperation relationship.Most institutions were concentrated in universities and a few in hospitals.

Analysis of Authors and Co-Cited AuthorsThe top 10 authors have collectively published a total of 198 papers,accounting for 24.06% of all published papers on MTM research.Ohno-Mastui K was identified as the most active author in the field of MTM research with 47 publications,followed by Chen Y, and Wang Y.Author co-citation levels were considered to reflect authors’ academic influence in a certain field.Ikuno Y ranked the highest in citation counts(n=271), followed by Ohno-Mastui K (n=237), Shmada N(n=226), Pannozo G (n=224) and Spaide RF (n=188).The top five cited authors in centrality were Akiba J, Grossniklaus HE,Gass JDM, Curtin BJ, and Saw SM.

Analysis of KeywordsKeywords cluster map consisting of 465 nodes and 2015 links were generated through cluster analysis of MTM publications (Figure 3).The top 10 keywords in frequency and centrality are shown in Table 1.As shown in Figure 3, the closer the research timeline view color is to the warm tones (orange and red), the more recent the study is.Optical coherence tomography angiography (OCTA), optical coherence tomography (OCT), macular hole, high myopia,macular buckling (MB) are the focus of the current research.Analysis of the frequency and centrality of keywords is believed to reflect the research trends.Keywords with the strongest citation burst potentially reveal hotspots and emerging trends in the research field.In recent years, progression (refers to the progression nature of pathological myopia, posterior staphyloma and MTM), association [refers to Genomewide association study (GWAS)], classification (refers to the classification of MTM) and shape (refers to the shape of sclera wall and posterior fundus) have become major research frontiers (Figure 4).

Figure 4 Top 25 keywords with the strongest citation bursts.

Co-citation relationship refers to two or more articles that are cited by one or more articles at the same time.Cluster analysis of co-cited references often reveals the common concerns of the literature and thus potentially reflects the research frontiers in a certain study field.The top five citations were articles published respectively by the following authors.Ruiz-Medranoet al[4]in 2019 proposed a new classification and grading system for MTM, taking atrophic (A), tractional (T)and neovascular (N) components into accounts.Holdenet al[5]in 2016 published a Meta-analysis, estimating that 938 million people would be affected by high myopia by 2050.Ohno-Matsuiet al[6-7]in 2016 performed a review about current understanding of the various ocular complications in high myopia, and they also proposed another classification system for myopic maculopathy in 2015, in which myopic maculopathy were divided into 5 categories, from “no myopic retinal degenerative lesion” (category 0) to “macular atrophy”(category 4).Shirohanaet al[8]in 2018 analyzed 729 eyes using ultrawide-field swept-source OCT, and described the association between posterior staphylomas and macular retinoschisis.They found that the epiretinal membranes or vitreoretinal attachments might act together with staphylomas as causative factors for macular retinoschisis.

Table 1 The top 10 keywords related to myopic traction maculopathy

DISCUSSION

MTM is a spectrum of complications of PM.PM is characterized by excessive axial elongation which causes deformations of the posterior segment of the eye and leads to visual impairment[9].The prevalence rate for PM is expected to keep rising in the years ahead[10], making PM associated ocular disorders one of the leading causes of irreversible vision loss.According to our analysis, during the preceding 17y, the number of annual publications in MTM research increased gradually,indicating that MTM continues to be a major concern of global researchers.

PM often occurs in high myopes[10].Globally, the prevalence rate of high myopia ranges from 1% to 4.7%[11], reaching its highest in East Asia with a prevalence rate of 2.6%-5.5%[12].Previous study reported that up to 35.0% high myopes suffered from MTM[2], and East Asia is also the region with the highest incidence of MTM.This is consistent with the country/region publication volume in our analysis that Asia (mainly China and Japan) ranked the first in publication volume.The institution analysis also indicates that universities in Asia (Tokyo Medical and Dental University, Capital Medical University, and Sun Yat-sen University) were the most active institutions.The cooperation map of countries and institutions, however, showed that the global research of MTM was relatively scattered.Only a few countries and institutions had built a limited cooperative relationship.Considering the high incidence of MTM and PM, and severe complications caused by them, it is necessary to establish closer research partnerships and improve the efficiency of international MTM research.

The research hotspots and frontiers of MTM over the past 17y were summarized based on the results of keywords cluster analyses.The progression nature of MTM, detection and examination for MTM, proper classification of MTM and surgical therapy for MTM are the major concerns in this field.MTM is increasingly recognized of its progressive nature[13].Shimadaet al[14]described the progression of MTM as an increasing of height and extent of schisis, or the development of a lamellar macular hole, full-thickness macular hole, or foveal detachment.The progression rate of MTM varies among different studies, from 11.6% to 68.9%.Shimadaet al[15]studied 207 eyes with MTM over a mean follow-up period of 36.2mo.MTM progression was found in 26 eyes (11.6%),and the rate was even higher in stage 4 (S4) eyes (eyes with entire macular area retinoschisis), with a reported rate of 42.9%.Gaucheret al[16]found that 68.9 % (20/29 eyes) of the eyes with foveoschsis progressed with enlargement of retinal cleavage and/or visual decline, during a mean followup period of 31.2mo.Recently, Liet al[17]reported that 43.4%MTM eyes (49/113) evolved over a mean follow-up period of 38.2mo.The mechanism of MTM progression has not yet been fully revealed, and the risk factors were reported to be age, excessive elongation of axial length (AL), posterior staphyloma, stiffinternal limiting membrane (ILM), epiretinal membrane, vitreous adhesion, and chorioretinal atrophy[18-20].The relationship between MTM and axial elongation has long been observed[21].Previous studies reported that a long AL was an independent risk factor of MTM[22].However, an excessive elongation of AL may not be enough on its own to cause MTM.Paroliniet al[23]found no direct correlation between the MTM stage and AL.They further hypothesized that it was the scleral wall shape, rather than the AL itself, that influenced the MTM stage.They retrospectively reviewed 321 eyes and identified 281 eyes with MTM and found that tractional changes were related to posterior staphyloma location and distribution.Yuet al[24]also found a significant difference in eye shape between MTM and non-MTM eyes.Most MTM eyes had non-uniform expansion of the eyeball, while non-MTM eyes usually had a uniform expansion[25].Changes in eye shape instead of axial elongation itself, may stretch the foveal area and the surrounding retina and thus cause MTM.

Choroidal atrophy is another factor that may affect MTM progression.Choroid thickness is known to be thinner in highly myopic eyes than in normal eyes[26].Researchers found that choroidal thickness patterns were distinctly different in eyes with myopic maculopathy, compared with those in normal eyes and high myopia eyes with normal fundus[27-28].These findings indicated that the choroidal thickness was negatively correlated with severity of myopic maculopathy.The Singapore Epidemiology of Eye Diseases-2 study group reported that MTM was significantly associated with macular chorioretinal atrophy.They explained that in the areas of advanced chorioretinal atrophy, the inner retina-posterior sclera attachment was weak and traction force might facilitate the dissociation of the retinal tissue in these areas[29].Previous studies supported the hypothesis that choroidal atrophy might contribute greatly to the pathogenesis of myopic maculopathy.Choroid attenuation may serve as a predictor of the development of advanced myopic maculopathy in high myopia children[30].However, the role of the choroid in MTM has not been fully elucidated.More studies on choroid morphological changes, choriod vessels, choroidal blood flow, as well as choroid thickness changes may help to reveal the relationship between choroid and MTM.

Recently, the genetic background for PM and myopic maculopathy has been brought to forefront.Hosodaet al[31]identifiedCCDC102Bas a susceptibility gene for myopic maculopathy in GWAS in 2018, which was not significantly associated with myopia itself.This finding suggests that myopic maculopathy may have a different gene background from high myopia.In 2022, Kassamet al[32]assessed the effectiveness of polygenic risk scores (derived from the largest GWAS of myopia in Europeans) in predicting the risk of myopic macular degeneration in a total of 5894 subjects and found that it was a valid predictor in identifying high risk population for high myopia and myopic macular detachment[32].These encouraging findings indicate that myopic maculopathy might be predicted and prevented, even in patients who already suffer from high myopia.The gene background of myopic maculopathy and PM remains mostly unknown.GWASs on fundus shape, staphyloma and choriod atrophy might be able to identify susceptibility genes associated with MTM, but not with high myopia, and thus contribute to the predicting and control of the development of myopic maculopathy.

The detection and examination methods of MTM have always been evolving.MTM was extremely difficult to be observed due to limitations of fundoscopy, the high transparency nature of retina and the thinning of choroid in high myopic eyes.Therefore, MTM was widely believed to be the tractional aspect of PM for many years.However,the advent and development of OCT changed the cognition.MTM is now recognized as a single clinical disorder with a spectrum of pathological changes[33-36].Recent advances in OCT technology, including enhanced depth imaging OCT and swept source OCT, are able to provide high resolution images and enable researchers to obtain reliable and stable measurements of choroid[8].The advent of OCTA further enables authors to detect retino-choroidal capillaries blood flow impairment in a non-invasive way[37-40].With the help of OCT/OCTA technology, authors are able to observe early signs of MTM, which were previously difficult to detect.However,the interpretation of choroidal circulation exhibited by OCTA images remains a challenge in PM eyes.Further studies are needed to reveal the relationship of choroidal circulation and MTM pathogenesis.

MTM classification evolves with the development of new technologies.Proper classification provides guidance to the timing of intervention and treatment strategies for MTM.Shimadaet al[14]first divided the progression process of MTM into 4 stages, form focal irregularity of external retina (S1) to retinal detachment resulted from outer macular hole (S4).The same group in 2013 proposed a classification system defining the progression of myopic retinoschsis as 5 stages: from stage 0, no maculoschisis to S4, entire macular area schisis[15].Ruiz-Medranoet al[4]formulated the ATN classification system based on three fundus manifestations: atrophy, traction,and neovascularization.In their system, macular tractional changes were divided into five stages: inner or/and outer foveoschisis, foveal detachment, macular hole, and retinal detachment.Recently, Paroliniet al[23]proposed the MTM Staging System which emphasized on the progressive nature of MTM.MTM were described as Stage 1, the inner or innerouter maculoschisis; Stage 2, outer maculoschisis; Stage 3,maculoschisis-detachment; Stage 4 macular detachment and the disappear of schisis.Each stage was further divided into 3 patterns according to foveal profiles: intact fovea structure(stage a), fovea inner lamellar macular hole (stage b) and fovea full-thickness macular hole (stage c).Based on this classification system, the authors suggested that eyes with stages 1a and 2a MTM should be followed for 2y, while eyes in other stages and patterns should be given surgical interventions[41].

There are two main surgical approaches in treating MTM:episcleral approach, including posterior scleral reinforcement and MB; and intraocular approach, including pars plana vitrectomy (PPV), with or without peeling of ILM, and the use of various endotamponade.Shevelev first reported transplantation of material for sclera reinforcement.Since then, many studies had published revision and modification of MB[42].As MB was proved to be able to compensate for the perpendicular force caused by axial elongation and posterior staphyloma, it was considered the criterion for the treatment of MHRD before 1980s[43].In the following years, PPV emerged to be a promising new technology as tangential and centripetal traction on vitreoretinal surface was proved to be an important factor in the pathogenesis of MTM.However, the success rate of PPV in high myopic macular detachment remains limited,with a high rate of reopen or failed macular hole, recurrence of retinal detachment and the risk of inducing iatrogenic macular hole[44-46].The unsatisfactory surgical results of PPV led to reconsideration of MB[47].Researchers reported that MB had a higher reattachment rate in treating the myopic MHRD compared with PPV[48].Some authors proposed that combining PPV+ILM maneuvers and MB might be able to yield more beneficial results.Caoet al[49]performed a Meta-analysis of the efficiency of combined PPV and posterior sclera reinforcement in treating MTM.They reported that 80% of patients had best corrected visual acuity improvement, 93% had retinal reattachment and 65% had macular hole closed, as well as decreased central foveal thickness.In that study, the average AL shortening was 1.74 mm.Paroliniet al[41]retrospectively reviewed 157 MTM eyes after MB or PPV or combined surgery, and concluded that PPV is better in addressing the tangential traction existing on the vitreo-retinal surface, while MB is better in resolving the perpendicular traction induced by posterior staphyloma.As the PPV and MB focus on two different aspects of the MTM pathology, surgeons should select proper approaches according to the MTM stages and classifications, separately or combined[50-52].

In conclusion, in order to provide an insight into the evolving trend of MTM research, we reviewed MTM research history in the past 17y using the visualization software CiteSpace,and analyzed MTM research strengths, research hotspots, and frontiers for MTM research, which may guide new directions for further study.

To the best of our knowledge, this is the first bibliometric analysis on MTM, In their bibliometric analysis on myopia in 2022, Wanget al[53]selected 100 most influential publications,with the research orientation mainly on refractive surgery,epidimiology, and etiology of myopia.Zhanget al[54]published bibliometrics analysis on PM in 2022 and dentified“choroidal neovascularization”, “bevacizumab”, “intravitreal injection” and “photodunamics therapy” as hot topics for high myopia research, these research directions represents the neovascular aspect of high myopia.These researchers all focused on myopia and high myopia, different from our research hotspots and fronts.The main study outcomes were as follows: 1) described the potential collaborators network of the main research field to provide references for strengthening international cooperation and exchanges; 2) followed frontiers and emerging trends in MTM research, and studies on the progression nature of MTM, genome-wide association study and proper classification of MTM might still be the frontiers of MTM researches; 3) identified the hotspots of MTM researches.OCT/OCTA, macular hole, high myopia, and MB are the focus of current studies; 4) OCT based classification may guide clinical strategies for the treatment of MTM.

There are some limitations of this study.First, we selected the literature in the WOS database, while literature in other databases may be excluded, thus researches concerning MTM may not be fully covered.Second, as the literature search was conducted in Jan.2023, some newly published researches could not be covered.

ACKNOWLEDGEMENTS

Foundation:Supported by Sichuan Administration of Traditional Chinese Medicine (No.2021MS422).

Conflicts of Interest: Zhang HD,None;Zhang L,None;Han F,None;Lin N,None;Jiang W,None.