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The AC/A ratio, age and presbyopia

K J Ciuffreda¹, M Rosenfield, H W Chen

¹Department of Vision Sciences, SUNY/State College of Optometry, New York 10010, USA.

Ophthalmic & Physiological Optics : the Journal of the British College of Ophthalmic Opticians (Optometrists)

|July 1, 1997

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Age does not significantly alter the accommodative convergence/accommodation (AC/A) ratio, particularly when excluding presbyopic individuals. This study clarifies previous equivocal findings on age-related changes in binocular vision.

Area of Science:

Ophthalmology
Optometry
Vision Science

Background:

Previous research on the impact of aging on the accommodative convergence/accommodation (AC/A) ratio has yielded inconsistent results.
Understanding age-related changes in binocular vision is crucial for diagnosing and managing visual disorders.

Purpose of the Study:

To investigate the effects of age on both the stimulus (AC/As) and response (AC/Ar) ratios.
To clarify the relationship between age and the AC/A ratio in a diverse age group.

Main Methods:

Employed a subjective haploscope-optometer to measure AC/As and AC/Ar in 42 participants aged 22-65 years.
Analyzed data to identify age-related trends in both stimulus and response ratios.
Segmented analysis based on age groups, including exclusion of presbyopic individuals.

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Main Results:

A minor but significant decrease in AC/As was observed with age.
AC/Ar showed a small increase with age in subjects under 45, but this trend disappeared when excluding mid-aged and early presbyopes.
Reliable AC/Ar assessment was not possible in subjects aged 45 and older due to physiological and instrumentation noise.

Conclusions:

The AC/A ratio appears to remain relatively constant with age when accounting for presbyopia and potential non-linearities in accommodation.
Findings support the Hess-Gullstrand theory of presbyopia.
Age-related changes in AC/Ar may be attributed to neural adaptation or accommodation non-linearities rather than a true alteration in the ratio.