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Br J Ophthalmol doi:10.1136/bjophthalmol-2012-301589
  • Clinical science

Survey of systematic reviews and meta-analyses published in ophthalmology

  1. Vishal Jhanji1,2,3
  1. 1Joint Shantou International Eye Center, Shantou University & The Chinese University of Hong Kong, Shantou, China
  2. 2Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong
  3. 3Centre for Eye Research Australia, University of Melbourne, Melbourne, Australia
  1. Correspondence to Dr Vishal Jhanji, Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong 123456, Hong Kong; vishaljhanji{at}gmail.com
  1. Contributors HC and VJ contributed equally to the study.

  • Accepted 5 March 2012
  • Published Online First 24 March 2012

Abstract

Purpose To analyse the types of systematic reviews and meta-analyses published in the field of ophthalmology.

Methods The systematic reviews and meta-analysis in ophthalmology published in peer-reviewed journals were retrieved. The distribution of systematic reviews and meta-analyses in various ophthalmic subspecialties, type of study and country of origin were determined.

Results A total of 533 records were identified as systematic reviews and meta-analysis in ophthalmology. Overall, retina and glaucoma were the two major subspecialties accounting for 35% and 21% of the published systematic reviews and meta-analyses, respectively. The major topics published in retina were age-related macular degeneration (37%), tumours (14%), and diabetic retinopathy (12%). More than half (56%) the systematic reviews and meta-analyses were interventional. The author affiliations of these studies were largely from the USA (30%) and the UK (22%). About 60% of the systematic reviews and meta-analyses were published in ophthalmology journals, followed by the Cochrane Library (15.75%) and other non-ophthalmic journals (25.14%), respectively. The number of publications increased from 3 per year in 1994 to almost 100 per year in 2010.

Conclusions The number of published systematic reviews and meta-analyses has been increasing progressively over the past few years. Retina and glaucoma are the two most commonly published topics. Non-ophthalmology journals form a sizeable proportion of avenues for ophthalmic publications.

Introduction

Peer-reviewed literature remains the standard way of reaching the scientific community all over the globe in order to broaden the base of evidence-based medicine.1–3 Over the past few years, professionals rendering services to patients are being asked to consider research evidence as part of their clinical and educational decision making. Systematic reviews and meta-analyses form an integral part of this evidence-based practice. The recent growth in the numbers of published systematic reviews reflects the growing recognition of their importance in delivering adequate healthcare. A systematic literature review is a means of evaluating and interpreting available research relevant to a particular research question or area of interest. These reviews provide practitioners an access to pre-filtered evidence that has been reviewed and methodically presented by an expert in a particular area.4 The knowledge base presented in a review limits systematic bias and reduces the time required to locate and appraise individual studies.5

Evidence-based medicine is further popular due to advances in science and technology coupled with new means of dispersal of knowledge. In the present study, we analysed the number of systematic reviews and meta-analyses that have been published in the field of ophthalmology.

Methods

Literature search was performed to screen all systematic reviews and meta-analyses published in ophthalmology journals in PubMed, EMBASE and Cochrane Library. Specifically, the following keywords were used on PubMed: (‘systematic analysis’ OR ‘systematic literature review’ OR ‘systematic literature analysis’ OR ‘systematic analysis’ OR ‘meta analysis’ OR ‘systematic review’ OR ‘meta-analysis’ OR ‘meta analyses’) AND (((‘Ophthalmology’ (Journal) OR ‘Acta Ophthalmol’ (Journal) OR ‘Acta Ophthalmol Scand’ (Journal) OR ‘Acta Ophthalmol Suppl (Oxf)’ (Journal) OR ‘Arch Ophthalmol’ (Journal) OR ‘Br J Ophthalmol’ (Journal)) OR ‘Clin Experiment Ophthalmol’ (Journal) OR ‘Can J Ophthalmol’ (Journal) OR ‘Cornea’ (Journal) OR ‘Curr Eye Res’ (Journal) OR ‘Curr Opin Ophthalmol’ (Journal) OR ‘Doc Ophthalmol’ (Journal) OR ‘Eur J Ophthalmol’ (Journal) OR ‘Exp Eye Res’ (Journal) OR ‘Eye (Lond)’ (Journal) OR ‘Graefes Arch Clin Exp Ophthalmol’ (Journal) OR ‘Indian J Ophthalmol’ (Journal) OR ‘Int Ophthalmol’ (Journal) OR ‘Int Ophthalmol Clin’ (Journal) OR ‘Invest Ophthalmol Vis Sci’ (Journal) OR ‘Jpn J Ophthalmol’ (Journal) OR ‘J AAPOS’ (Journal) OR ‘J Cataract Refract Surg’ (Journal) OR ‘Korean J Ophthalmol’ (Journal) OR ‘Mol Vis’ (Journal) OR ‘Ocul Immunol Inflamm’ (Journal) OR ‘Ophthalmic Epidemiol’ (Journal) OR ‘Ophthalmic Genet’ (Journal) OR ‘Ophthalmic Res’ (Journal) OR ‘Prog Retin Eye Res’ (Journal) OR ‘Retina’ (Journal) OR ‘Surv Ophthalmol’ (Journal) OR ‘Vision Res’ (Journal)) OR (Journal of Glaucoma) OR (‘Am J Ophthalmol’ (Journal) OR ‘Ann Ophthalmol (Skokie)’ (Journal) OR ‘Cutan Ocul Toxicol’ (Journal) OR ‘J Neuroophthalmol’ (Journal) OR ‘J Ocul Pharmacol Ther’ (Journal) OR ‘J Pediatr Ophthalmol Strabismus’ (Journal) OR ‘J Refract Surg’ (Journal) OR ‘J Vis’ (Journal) OR ‘Ocul Surf’ (Journal) OR ‘Ophthalmic Physiol Opt’ (Journal) OR ‘Ophthalmic Surg Lasers’ (Journal) OR ‘Ophthalmic Surg Lasers Imaging’ (Journal) OR ‘Ophthalmologica’ (Journal) OR ‘Vis Neurosci’ (Journal)) OR (‘Clin Exp Optom’ (Journal)) OR (‘Optom Vis Sci’ (Journal)) OR ‘Neuro-ophthalmology’ (Journal)).

For EMBASE, we used (Cochrane review)/lim OR (meta analysis)/lim OR (systematic review)/lim AND (ophthalmology)/lim. Search in the Cochrane Library was based on topics of ‘Eyes and vision’.

The retrieved records were imported into Endnote software V. X4. The duplicated records and records without an abstract were excluded. Then the abstracts were reviewed and the records of other topics or non-systematic reviews were excluded. The following information was extracted from the records: subspecialty, type of original study, year and country of origin of manuscript. The proportion of each parameter was calculated.

Results

Overall, 352 records were retrieved from PubMed, 616 from EMBASE and 82 from the Cochrane Library up to the year 2010. With the function of Endnote software, 148 duplicate records and 124 records without an abstract were excluded. After reviewing the abstracts, 188 non-systematic reviews/meta-analysis and 57 records of other (non-ophthalmology) topics were excluded. A total of 533 records were selected for the final analysis (figure 1). The distribution of systematic reviews and meta-analyses in various ophthalmic subspecialties is depicted in table 1. Overall, retina and glaucoma were the two major subspecialties accounting for 35% and 21% of the published systematic reviews and meta-analyses, respectively.

Figure 1

Flow diagram showing the selection of published systematic reviews. This figure is produced in colour in the online journal. (Visit the website to view the colour figure).

Table 1

Overall distribution of systematic reviews and meta-analyses in various ophthalmic subspecialties until the year 2010

The major topics published on retina were age-related macular degeneration (37%), tumours (14%), diabetic retinopathy (12%), macular oedema (8%) and retinal vein occlusion (8%) (table 2).

Table 2

Distribution of topics of published systematic reviews and meta-analyses in retina until the year 2010

More than half (56%) the systematic reviews and meta-analyses were interventional. Other study designs included environmental risk factors, genetic risk factors, prevalence, diagnoses, screening and economics, case reports and natural history (table 3).

Table 3

Study designs used in systematic reviews and meta-analyses published in ophthalmology until the year 2010

The author affiliations were from USA (30%), UK (22%), China (10%), Australia, Germany, Canada, The Netherlands, Italy and Japan (table 4).

Table 4

Countries of origin of manuscripts published as systematic reviews and meta-analyses until the year 2010

More than half (n=317, 59.47%) the systematic reviews and meta-analyses were published in ophthalmology journals, while 15.38% (n=82) were published in the Cochrane Library. About a quarter of publications (n=134; 25.14%) appeared in 93 different non-ophthalmology journals. The total number of publications increased from 3 per year in 1994 to almost 100 per year in 2010 (figure 2).

Figure 2

Graph showing an increase in number of published systematic reviews and meta-analyses in ophthalmology from 1988 to 2010. This figure is produced in colour in the online journal. (Visit the website to view the colour figure).

Table 5 shows the breakdown of the number of systematic reviews and meta-analyses published from 1988 to 2010 according to the ophthalmic subspecialties.

Table 5

Number of systematic reviews and meta-analyses published in various ophthalmic subspecialties from 1988 up to 2010

Discussion

The present study is an endeavour to analyse the publishing trend of systematic reviews and meta-analyses that have been published in the field of ophthalmology. Our study found that the number of such publications has increased tremendously in the past 5 years. A majority of the publications were in the field of retina. This might be related to the renewed interest in the topics related to age-related macular degeneration, use of anti-vascular endothelial growth factor drugs and visual/functional outcomes in these patients. This also corroborates with a majority of the publications from USA where age-related macular degeneration is one of the leading causes of visual impairment. Furthermore, many of the publications were in the form of interventional trials which reflects the increased use of anti-vascular endothelial growth factor treatments. There was a steady increase in the number of publications after the year 2004. The major proportion of this increase was due to publications in retina and glaucoma, whereas, the number of publications in cataract and cornea remained mostly static.

A good proportion of publications were in non-ophthalmology journals. Many of the subspecialty journals, especially neuro-ophthalmology, genetics and endocrinology, have high-impact factors and, therefore, encourage submissions to all related medical fields. This is a representation of integration of medical knowledge and as a step to broaden the horizons of ophthalmic literature. Nearly 15% of the systematic ophthalmic reviews were published in the Cochrane Library.

Recently, Kumar et al analysed the subspecialty articles published in the top seven general clinical journals over a 5-year period.6 This study showed that medical retina is the most represented subspecialty in the literature. Our results match the findings of this study. Further, much like the results of the study by Kumar et al, we found that there were relatively few publications from ophthalmic subspecialties like neuro-ophthalmology, oculoplastics, uveitis and paediatrics. It is postulated by Kumar et al that these subjects appear more often in non-ophthalmology journals. However, we did not find an increased publication rate of these subspecialties even after including non-ophthalmic journals in our survey. Clearly, these are the areas that are in need of further funding, original research and systematic reviews in the near future.

The number of published systematic reviews and meta-analyses has increased steadily over the past decade.1 This corroborates well with the increase in the number of original high-quality research articles published in ophthalmology in the past few years.6 However, it is widely acknowledged that extensive labour is involved in publishing a quality systematic review.7 Even today, the demand for systematic reviews may exceed the capacity of those who are prepared to commit themselves to preparing reviews which meet adequate scientific standards. An interesting finding in our study was the steady rise in ophthalmic reviews published in the Cochrane Library. The Cochrane database was established in the year 1993 with an aim to make the results of well-conducted controlled trials readily available.1 It has grown tremendously since then and has been considered a key resource in evidence-based medicine. The Cochrane Database of Systematic Reviews has a 2010 impact factor of 6.186, ranking it 10th among 151 journals in the category Medicine, General & Internal.8 This further encourages the authors to publish research beyond the boundaries of ophthalmic journals.

Another factor that assumes importance in systematic reviews is the quality of these publications. Due to the collection of a large amount of data, there is increased room for error. Although this may be extremely laborious, analysis including these data would give a greater indication of the quality of research being performed. Comparisons can also be drawn between ophthalmic and non-ophthalmic journals. Furthermore, it is to be noted that the overall results can vary according to the disease and intervention definition used at the time of data collection. Perhaps a separate quality-based analysis of systematic reviews in ophthalmology would be desirable in future.

Footnotes

  • Funding Dr Haoyu Chen is supported by grants from the National Nature Science Foundation of China, Guangdong Science and Technology Project, Guangdong Medical Research Foundation, Science and Technology Project of Shantou City, China and, the Research Fund of Joint Shantou International Eye Center.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

References

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