Japan's share of published research in ophthalmology

Purpose: This study was conducted to determine Japan's share of published research in ophthalmology during the last decade. Methods: Ophthalmology journals with higher impact factors were accessed through the Medline database to elicit the number of articles published in 1991-2000 that originated in various countries, including Japan. The proportion of articles with a higher grade of evidence (randomized controlled trials/clinical trials, cohort studies, and case-control studies) was determined for Japan and compared with the average values of the total articles published in these journals. In addition, the percentage of published research from the 20 top-ranking countries was calculated, showing the trend over time. Results: Of the total articles (21,327), Japan's share in the selected ophthalmology journals was 6.5% (1,387 articles), ranking third in the world, following the USA (51.5%) and the UK (11.3%). The recent increase in the share was statistically significant for Japan (P = .01). However, the proportionate value of clinical research evidence was lower for Japan-originated articles than the average value for the total clinical research articles in these journals. Conclusions: Appropriate measures should be taken in the ophthalmology field in Japan to increase the number of clinical research papers with a higher grade of evidence.