Ocular DiseaseAssessment of visual function                                                         

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Course Summary

Dr Dan Rosser & David Cartwright (16:25)

Measuring visual acuity is a routine optometric test that we often take for granted. We might think it is an essentially objective test, but it’s more subjective than many of us realise, making it hard to achieve reliable and consistent results. Although most community optometrists continue to use the standard Snellen chart, logMAR and high and low contrast charts have emerged as alternatives, particularly in hospital practice. For those less familiar with these methods the differences in notation can make it difficult to put the results into context and to make useful clinical comparisons. Dr Dan Rosser is Principle Optometrist and Head of the Optometry Department at the Norfolk & Norwich University Hospital, here he discusses different methods of measuring visual acuity with David Cartwright, including the appropriate uses and associated difficulties of each.

First published in DOCET OQ88 (2013).

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    • An overview of the different methods of measuring visual acuity.
    • A comparative outline of the shortcomings and errors in each.
    • An indication of the advantages of different chart designs for different patient groups.
    • Advice on interpreting VA measurements taken with various different charts for community optometrists.

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      Measuring visual acuity

      Dr Dan Rosser & David Cartwright (16:25)

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      • Bourne R, et al. 2003. Evaluating a new logMAR chart designed to improve visual acuity assessment in population-based surveys. Eye 17 (6), 754-8.
      • Rosser D. 2006. Detecting clinical change using visual acuity measurements – the effect of uncorrected refractive error. Ophthalmic and Physiological Optics 26 (2), 214.
      • Saunders K. 2010. Testing visual acuity of young children: An evidence-based guide for optometrists. Optometry in Practice 11 (4), 161-168.


      Conversion table logMAR to Snellen:

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