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Related Experiment Videos

Low vision aids and the presbyope.

S M Dillehay1, C D Pensyl

  • 1Ohio State University, College of Optometry, Columbus 43210.

Journal of the American Optometric Association
|September 1, 1991
PubMed
Summary

Emerging light divergence from low vision devices significantly impacts magnification for presbyopic patients. This study found divergence is unpredictable and developed tables to simplify magnification calculations for low vision aids.

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Area of Science:

  • Ophthalmology and Vision Science
  • Optical Engineering

Background:

  • Presbyopic individuals using low vision devices require near addition to focus divergent light rays.
  • The interplay between light divergence and near addition power critically influences device magnification.

Purpose of the Study:

  • To investigate how varying emerging divergences and near addition powers affect the magnification of low vision devices.
  • To provide a simplified method for calculating magnification adjustments in low vision aids.

Main Methods:

  • Measured emerging divergence of 54 fixed focus stand magnifiers across different powers and manufacturers.
  • Employed trial lenses and a telescope for accurate divergence measurements.
  • Developed calculation tables to simplify magnification determination.

Main Results:

  • Emerging divergence from stand magnifiers was found to be unpredictable.
  • No correlation was established between magnifier power and emerging divergence.
  • Existing mathematical formulas for magnification calculation were simplified into practical tables.

Conclusions:

  • The unpredictable nature of light divergence necessitates practical tools for accurate magnification assessment.
  • Developed tables offer a simplified approach for clinicians and patients to determine magnification effects with low vision devices and near additions.

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