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Am J Ophthalmol. 2014 Jan;157(1):254-259.e1. doi: 10.1016/j.ajo.2013.09.013. Epub 2013 Nov 7.

Ophthalmic randomized controlled trials reports: the statement of the hypothesis.

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Department of Biostatistics, Singapore Clinical Research Institute, Singapore, Republic of Singapore; Center for Quantitative Medicine, Office of Clinical Sciences, Duke-National University of Singapore Graduate Medical School, Singapore, Republic of Singapore. Electronic address:
Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, Hong Kong Special Administrative Region, China; Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China.
School of Nursing, The University of Hong Kong, Hong Kong Special Administrative Region, China.



To evaluate whether the ophthalmic randomized controlled trials (RCTs) were designed properly, their hypotheses stated clearly, and their conclusions drawn correctly.


A systematic review of 206 ophthalmic RCTs.


The objective statement, methods, and results sections and the conclusions of RCTs published in 4 major general clinical ophthalmology journals from 2009 through 2011 were assessed. The clinical objective and specific hypothesis were the main outcome measures.


The clinical objective of the trial was presented in 199 (96.6%) studies and the hypothesis was specified explicitly in 56 (27.2%) studies. One hundred ninety (92.2%) studies tested superiority. Among them, 17 (8.3%) studies comparing 2 or more active treatments concluded equal or similar effectiveness between the 2 arms after obtaining insignificant results. There were 5 noninferiority studies and 4 equivalence studies. How the treatments were compared was not mentioned in 1 of the noninferiority studies. Two of the equivalence studies did not specify the equivalence margin and used tests for detecting difference rather than confirming equivalence.


The clinical objective commonly was stated, but the prospectively defined hypothesis tended to be understated in ophthalmic RCTs. Superiority was the most common type of comparison. Conclusions made in some of them with negative results were not consistent with the hypothesis, indicating that noninferiority or equivalence may be a more appropriate design. Flaws were common in the noninferiority and equivalence studies. Future ophthalmic researchers should choose the type of comparison carefully, specify the hypothesis clearly, and draw conclusions that are consistent with the hypothesis.

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