title: Trends in ophthalmology journals: a five-year bibliometric analysis (2009-2013).
abstract: OBJECTIVE
  To explore the trends in the ophthalmic literature over a 5-year period in relation to country, research expenditure and demographics.
  
  
  METHODS
  Articles published between 2009 and 2013 by the 20highest-contributing countries in the 20 top-ranked ophthalmology journals were identified by their country of affiliation. The number of articles published and mean impact factor were measured per country for each year and trends explored using regression analysis with 5-year and 10-year forecasts calculated. Data on research expenditure was collected and tested for correlation with the number of articles and mean impact factor.
  
  
  RESULTS
  The analysis included 19 338 articles. The USA, UK and Europe accounted for 60.2% of articles published, with the USA contributing 7388 articles (34.0%). The USA also demonstrated the highest mean impact factor (3.5). Research expenditure was significantly correlated with both research output (r=0.86,P<0.001) and scholarly impact (r=0.42,P<0.001). China (P<0.01), Korea (P<0.01) and India (P<0.02) demonstrated a significant growth in research output over the study period. The research contribution of these three countries combined is forecasted to overtake that of Europe within ten years, with China expected to be the second-largest contributor within five years. These countries were also among those demonstrating the greatest growth in research expenditure.
  
  
  CONCLUSIONS
  While the USA and European countries are major contributors of ophthalmic research, the productivity of some Asian countries is growing impressively. The contribution of China, Korea and India is forecasted to outweigh that of Europe by 2023. Research expenditure is highly correlated with research productivity and these trends reflect the differing economic priorities across the world.
authors.affiliation: Eye Unit, Royal Bournemouth Hospital, Bournemouth, BH7 7DW, UK.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Schulz
authors.affiliation: Department of Ophthalmology, Conquest Hospital, St. Leonards-on-Sea, TN37 7RD, UK.
authors.forename: Alasdair
authors.initials: A
authors.lastname: Kennedy
authors.affiliation: Department of Plastic Surgery, Queen Elizabeth Hospital, Birmingham, B15 2TH, UK.
authors.forename: Ben C
authors.initials: BC
authors.lastname: Rymer
keywords: bibliometrics; journal impact factor; ophthalmology