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Related Experiment Videos

Telescopes, light vergence, and accommodation

A N Freid

    American Journal of Optometry and Physiological Optics
    |June 1, 1977
    PubMed
    Summary

    Telescopes make near object focusing difficult. A new formula shows bifocal lenses or vertex distance changes are needed for effective near vision with telescope spectacles, aiding precise refractions.

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    Area of Science:

    • Ophthalmology
    • Optics
    • Vision Science

    Background:

    • The accommodative response is crucial for clear near vision.
    • Telescopic devices can alter the effective optical system, impacting accommodation.
    • Understanding these effects is vital for accurate vision correction.

    Purpose of the Study:

    • To explain the ineffectiveness of accommodation through telescopes.
    • To introduce a formula for calculating necessary optical adjustments.
    • To guide precise refractive measurements with telescopic aids.

    Main Methods:

    • Derivation and application of a simple optical formula.
    • Analysis of the accommodative demand with spectacle lens telescopes.
    • Comparison of refractions with and without telescopic devices.

    Main Results:

    • The accommodative response is significantly compromised when viewing near objects through a telescope.
    • A formula demonstrates the necessity of bifocal spectacle objectives or vertex distance modification for near viewing.
    • The derived formula enables more accurate comparison of refractions with and without telescopes.

    Conclusions:

    • Effective near vision correction with contact lens spectacle telescopes requires optical adaptation.
    • The formula provides a tool for clinicians to refine refractive assessments.
    • Refractions for driving with telescopes should be performed at distances of 20 feet or greater.

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