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Related Experiment Videos

Determining magnification for reading with low vision.

Allen C Y Cheong1, Jan E Lovie-Kitchin, Alex R Bowers

  • 1Centre for Eye Research, School of Optometry, Queensland University of Technology, Kelvin Grove, QLD, 4059, Australia.

Clinical & Experimental Optometry
|July 24, 2002
PubMed
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Calculating magnification for low vision aids using a fixed acuity reserve (0.3 log unit) is effective for experienced users. This method, along with individual assessment, ensures optimal reading rates and visual acuity with low vision devices.

Area of Science:

  • Ophthalmology
  • Low Vision Rehabilitation
  • Visual Optics

Background:

  • Traditional methods of calculating low vision aid magnification based on visual acuity (VA) often underestimated required magnification.
  • Recent research highlights the critical role of acuity reserve in achieving optimal reading rates.
  • Two approaches for determining acuity reserve exist: a fixed 0.3 log unit reserve or an individualized determination.

Purpose of the Study:

  • To investigate and compare magnification and reading rates using low vision aids selected by fixed versus individual acuity reserve methods.
  • To evaluate the effectiveness of these methods against the subjects' own prescribed low vision aids.

Main Methods:

  • Nineteen experienced low vision subjects with age-related macular degeneration (AMD) participated.

Related Experiment Videos

  • Near visual acuity (VA) and reading rates were measured with low vision aids selected by both fixed and individual acuity reserve methods.
  • These measures were compared to those obtained with the subjects' habitual low vision aids.

    • Main Results:

    • No significant differences were found in reading rates or near VA between aids selected by the fixed acuity reserve method, the individual acuity reserve method, or the subjects' own magnifiers.
    • Reading rates achieved with low vision aids were comparable to reading rates using large print with conventional reading additions.
    • Magnifiers do not appear to reduce reading rates in experienced low vision users.

    Conclusions:

    • The fixed acuity reserve method (0.3 log unit) is a simple and recommended approach for calculating required magnification for low vision patients, requiring only near VA and print size.
    • Individual assessment of acuity reserve is advised if the fixed method does not yield satisfactory near VA or reading rates.
    • Experienced low vision users can achieve effective reading with prescribed magnifiers without compromising reading speed.