Statistical guidelines for the analysis of data obtained from one or both eyes

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  • Richard A. Armstrong

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Abstract

Purpose - Measurements obtained from the right and left eye of a subject are often correlated whereas many statistical tests assume observations in a sample are independent. Hence, data collected from both eyes cannot be combined without taking this correlation into account. Current practice is reviewed with reference to articles published in three optometry journals, viz., Ophthalmic and Physiological Optics (OPO), Optometry and Vision Science (OVS), Clinical and Experimental Optometry (CEO) during the period 2009–2012.

Recent findings - Of the 230 articles reviewed, 148/230 (64%) obtained data from one eye and 82/230 (36%) from both eyes. Of the 148 one-eye articles, the right eye, left eye, a randomly selected eye, the better eye, the worse or diseased eye, or the dominant eye were all used as selection criteria. Of the 82 two-eye articles, the analysis utilized data from: (1) one eye only rejecting data from the adjacent eye, (2) both eyes separately, (3) both eyes taking into account the correlation between eyes, or (4) both eyes using one eye as a treated or diseased eye, the other acting as a control. In a proportion of studies, data were combined from both eyes without correction.

Summary - It is suggested that: (1) investigators should consider whether it is advantageous to collect data from both eyes, (2) if one eye is studied and both are eligible, then it should be chosen at random, and (3) two-eye data can be analysed incorporating eyes as a ‘within subjects’ factor.

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  • Statistical guidelines for the analysis of data

    Rights statement: Ophthalmic & Physiological Optics © 2012 The College of Optometrists. Acknowledgement to Blackwell Publishing The definitive version is available at www.onlinelibrary.wiley.com

    Accepted author manuscript, 217 KB, PDF-document

Details

Original languageEnglish
Pages (from-to)7-14
Number of pages8
JournalOphthalmic and Physiological Optics
Volume33
Issue number1
Early online date17 Dec 2012
DOIs
Publication statusPublished - Jan 2013

Bibliographic note

Ophthalmic & Physiological Optics © 2012 The College of Optometrists. Acknowledgement to Blackwell Publishing The definitive version is available at www.onlinelibrary.wiley.com

    Keywords

  • Clinical and Experimental Optometry, One eye or two, Ophthalnic and physiological optics, Optometry and vision science, Statistical guidelines

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