Use of statistical analyses in the ophthalmic literature.

Purpose: To identify the most commonly used statistical analyses in the ophthalmic literature and to determine the likely gain in comprehension of the literature that readers could expect if they were to add knowledge of more advanced techniques sequentially to their statistical repertoire.

Design: Cross-sectional study.

Methods: All articles published from January 2012 through December 2012 in Ophthalmology, the American Journal of Ophthalmology, and Archives of Ophthalmology were reviewed. A total of 780 peer-reviewed articles were included. Two reviewers examined each article and assigned categories to each one depending on the type of statistical analyses used. Discrepancies between reviewers were resolved by consensus.

Main Outcome Measures: Total number and percentage of articles containing each category of statistical analysis were obtained. Additionally, we estimated the accumulated number and percentage of articles that a reader would be expected to be able to interpret depending on their statistical repertoire.

Results: Readers with little or no statistical knowledge would be expected to be able to interpret the statistical methods presented in only 20.8% of articles. To understand more than half (51.4%) of the articles published, readers would be expected to be familiar with at least 15 different statistical methods. Knowledge of 21 categories of statistical methods was necessary to comprehend 70.9% of articles, whereas knowledge of more than 29 categories was necessary to comprehend more than 90% of articles. Articles related to retina and glaucoma subspecialties showed a tendency for using more complex analysis when compared with articles from the cornea subspecialty.

Conclusions: Readers of clinical journals in ophthalmology need to have substantial knowledge of statistical methodology to understand the results of studies published in the literature. The frequency of the use of complex statistical analyses also indicates that those involved in the editorial peer-review process must have sound statistical knowledge to appraise critically the articles submitted for publication. The results of this study could provide guidance to direct the statistical learning of clinical ophthalmologists, researchers, and educators involved in the design of courses for residents and medical students.