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Related Experiment Video

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Clinical Application of Phase Angle and BIVA Z-Score Analyses in Patients Admitted to an Emergency Department with Acute Heart Failure
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The Gradient AC/A Ratio: What's Really Normal?

Jorie Hart Jackson, Kyle Arnoldi

    The American Orthoptic Journal
    |December 15, 2010
    PubMed
    Summary

    The Gradient and Clinical methods for measuring the accommodative convergence/accommodation (AC/A) ratio differ significantly. This study found discrepancies between the two methods in patients with acquired nonparalytic esotropia.

    Area of Science:

    • Ophthalmology
    • Optometry
    • Vision Science

    Background:

    • The accommodative convergence/accommodation (AC/A) ratio is crucial for understanding binocular vision anomalies.
    • The Gradient Method and Clinical Method are common but distinct approaches to measuring the AC/A ratio.
    • Interchangeable use of these methods may lead to diagnostic inaccuracies.

    Purpose of the Study:

    • To prospectively compare the Gradient AC/A and Clinical AC/A methods.
    • To evaluate Gradient AC/A calculations using minus (stimulating accommodation) and plus (relaxing accommodation) lenses.
    • To assess these methods in patients with acquired nonparalytic esotropia.

    Main Methods:

    • Prospective study of 69 consecutive patients with acquired nonparalytic esotropia.

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  • Gradient AC/A measured by stimulating and relaxing accommodation.
  • Clinical AC/A assessed by detecting distance-near esotropia disparities.

    • Main Results:

    • Mean Gradient AC/A was 2:1 for normal Clinical AC/A and 5:1 for high Clinical AC/A.
    • 44% of patients with high Clinical AC/A showed normal/low Gradient AC/A, suggesting nonaccommodative convergence excess.
    • Gradient AC/A measurements were statistically identical whether using minus or plus lenses.

    Conclusions:

    • Significant differences exist between Gradient and Clinical AC/A measurements in this patient cohort.
    • A substantial proportion of patients with high Clinical AC/A may have underlying nonaccommodative convergence excess.
    • Both minus and plus lens methods for Gradient AC/A yield comparable results.