Predicting prescribed magnification


Aim: To determine the best method of estimating the optimum magnification needed by visually impaired patients. Methods: The magnification of low vision aids prescribed to 187 presbyopic visually impaired patients for reading newspapers or books was compared with logMAR distance and near acuity (at 25 cm) and magnification predicted by +4 D step near additions. Results: Distance letter (r = 0.58) and near word visual acuity (r = 0.67) were strongly correlated to the prescribed magnification as were predictive formulae based on these measures. Prediction using the effect of proximal magnification resulted in a similar correlation (r = 0.67) and prediction was poorer in those who did not benefit from proximal magnification. The difference between prescribed and predicted magnification was found to be unrelated to the condition causing visual impairment (F = 2.57, p = 0.08), the central visual field status (F = 0.57, p = 0.57) and patient psychology (F = 0.44, p = 0.51), but was higher in those prescribed stand magnifiers than high near additions (F = 5.99, p < 0.01). Conclusions: The magnification necessary to perform normal visual tasks can be predicted in the majority of cases using visual acuity measures, although measuring the effect of proximal magnification demonstrates the effect of stronger glasses and identifies those in whom prescribed magnification is more difficult to predict.

Publication DOI:
Divisions: College of Health & Life Sciences > School of Optometry > Optometry
College of Health & Life Sciences > School of Optometry > Optometry & Vision Science Research Group (OVSRG)
College of Health & Life Sciences
College of Health & Life Sciences > School of Optometry > Vision, Hearing and Language
Additional Information: Conference on Multi-Disciplinary Low Vision Rehabilitation and Research, Aston, England, December 2003. The definitive version is available at © 2004 The College of Optometrists. Published by Blackwell.
Uncontrolled Keywords: low vision,magnification,prediction,visual acuity,visual impairment,Ophthalmology,Sensory Systems,General Health Professions
Publication ISSN: 1475-1313
Last Modified: 28 Jun 2024 08:27
Date Deposited: 11 Mar 2019 17:35
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL) ... 775350/abstract (Publisher URL)
PURE Output Type: Article
Published Date: 2004-07
Authors: Wolffsohn, James S.W. (ORCID Profile 0000-0003-4673-8927)
Eperjesi, Frank (ORCID Profile 0000-0003-4358-0095)



Version: Accepted Version

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