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M. A. Williams, T. N. Moutray, A. J. Jackson; Uniformity of Measuring Visual Acuity in Published Studies. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2537.
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To investigate methods used in contemporary ophthalmic literature to designate visual acuity (VA).
Papers in all 2005 editions of five ophthalmic journals were considered. Papers were included if VA or vision was mentioned in the abstract and if the study related to age-related macular degeneration, cataract or refractive surgery. If a paper was selected on the basis of its abstract, the full text of the paper was examined for details on types of chart used to measure VA, means of expressing VA in results and specifics concerning chart features, testing protocols and data analysis.
One hundred and thirty-two papers were included. The most common means of referring to VA measurement in methods sections was merely as "Best Corrected Visual Acuity" (34.8%; n=46/132). When chart type was mentioned, the most commonly specified charts were LogMAR acuity (32.6%; n=43/132) and Snellen (24.2%, n=32/132). The commonest ways in which acuity measurements were presented in the results sections were as Snellen fractional (47.0%; n=62/132) and LogMAR (22.0%;n=29/132). Most papers gave no details regarding chart features, testing protocols or data analysis. Twenty-one studies stated that VA data was transformed into another notation to facilitate statistical analysis.
Substantial diversity exists in the information given regarding the measurement of VA, and in the means by which VA is measured, analysed and expressed. Sufficient detail should be given on VA measurement to enable others to duplicate the research. We suggest that LogMAR-based charts should always be used to measure vision in prospective studies and their use encouraged in clinical settings. Transforming VA data for results and analysis is hazardous.
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