The AC/A Ratio and Age—A Longitudinal Study

Eskridge, Jess B.

doi:10.1097/00006324-198311000-00007

Cited by 14 publications

(10 citation statements)

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“…Bruce, Atchison and Bhoola 200 found that, for subjects aged between 15 and 45 years, the response AC/A ratio increased with age and the response CA/C ratio decreased. Broadly compatible results for the same ratios have been found by other authors, although extending over slightly different age ranges 201,202 . Ciuffreda, Rosenfield and Chen 203 found a similar marked increase in response AC/A between the ages of 20 and 45 years but there was no significant change when they restricted their analysis to subjects between 20 and 35 years of age.…”

Section: Presbyopiasupporting

confidence: 86%

“…Broadly compatible results for the same ratios have been found by other authors, although extending over slightly different age ranges. 201,202 Ciuffreda, Rosenfield and Chen 203 found a similar marked increase in response AC/A between the ages of 20 and 45 years but there was no significant change when they restricted their analysis to subjects between 20 and 35 years of age. Overall, the evidence favours an increase in response AC/A through pre-presbyopic adult life, a characteristic of some importance in relation to theories of presbyopia, as it suggests that increased innervation is required in the older eye to produce the same accommodation response (see below).…”

Section: Changes In Other Aspects Of Accommodation With Agementioning

confidence: 87%

“…Moreover, there is ample evidence that greater force is required to produce a given change in accommodation as the eye ages 30,230 . Changes such as the observed increase in response AC/A ratio with age 199–202 also appear to refute the Hess‐Gullstrand theory. Studies like those of Fisher 214,216,217 and Glasser and Campbell 30,205 suggest that, as the eye ages, greater force will need to be exerted on the lens and capsule to achieve the same change in accommodation, thus supporting the basic Duane‐Fincham model.…”

Section: Presbyopiamentioning

confidence: 96%

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The eye in focus: accommodation and presbyopia

Charman

2008

Clinical and Experimental Optometry

207

136

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Current understanding of the anatomy, function and performance of the accommodative system of the young, adult human eye is outlined. Most major current models of the accommodative mechanism are based on Helmholtz's original ideas but, despite of a growing volume of related research, uncertainty continues over the relative contributions made to the overall mechanism by different ocular structures. The changes with age are then discussed. Although the amplitude of accommodation decreases steadily from later childhood, the speed and accuracy of the system within the available amplitude are little impaired until the age of about 40, when the amplitude falls below that needed for normal near work. A review of the available evidence on age-related change in the lens, capsule, ciliary body and other relevant ocular structures confirms that geometric and viscoelastic lenticular changes play major roles in the progressive loss of accommodation. Other factors may also contribute in an, as yet, unquantified way and a full understanding of the origins of presbyopic change remains elusive.

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Section: Presbyopiasupporting

confidence: 86%

Section: Changes In Other Aspects Of Accommodation With Agementioning

confidence: 87%

Section: Presbyopiamentioning

confidence: 96%

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The eye in focus: accommodation and presbyopia

Charman

2008

Clinical and Experimental Optometry

207

136

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“…An increase in the response AC/A ratio and a decrease in the CA/C (convergence accommodation/convergence) ratio with the decline in the amplitude of accommodation has been shown in previous studies [2,3,11,16], most recently that of Bruce et al [3], who found a decrease in the CA/C ratio of around 0.018 D/MA (dioptre/metre-angle) per year and an increase in the response AC/A ratio of 0.02 MA/D (metre-angle/dioptre) per year. One metre-angle is the convergence required to fixate an object at 1 m; an angle y in metre-angles can be converted to prism dioptres using the equation z=y.PD, where PD is the inter-pupillary distance in centimetres and z is the angle in prism dioptres.…”

Section: Introductionsupporting

confidence: 57%

The effect of incipient presbyopia on the correspondence between accommodation and vergence

Baker

Gilmartin

2002

Graefe's Arch Clin Exp Ophthalmol

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The results of this study fail to support the Hess-Gullstrand theory of presbyopia in that the ciliary muscle effort required to produce a unit change in accommodation increases, rather than stays constant, with age. Data show that the near vision response is limited to the maximum vergence response that can be tolerated and, despite being within the amplitude of accommodation, a stimulus may still appear blurred because the vergence component determines the proportion of available accommodation utilised during near vision.

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“…However, the four studies which have reported changes in the response AC/A ratio with age had a number of significant limitations. First, two were longitudinal investigations involving only a single subject (the respective authors) (Fry, 1959;Eskridge. 1983).…”

Section: Introductionmentioning

confidence: 99%

The AC/A ratio, age and presbyopia

1997

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Previous reports concerning the effect of age on the AC/A ratio have been equivocal. Therefore, the present study investigated both the stimulus (AC/As) and response (AC/Ar) ratios using a subjective haploscope-optometer in a relatively large sample of subjects (n = 42) over a wide range of ages (22-65 years). The AC/As showed a small but significant decrease with age (approximately 0.04 delta/D/year). When the older subjects (> 45 years of age) were excluded, however, there was no systematic age effect. The AC/Ar exhibited a small but significant increase with age (approximately 0.08 delta/D/year) for subjects under 45 years of age. However, when the older pre-presbyopes and younger presbyopes (35-44 years of age) were excluded, there was no systematic age effect. In subjects 45 years of age and older, the AC/Ar could not be reliably assessed. This was attributed to physiological and instrumentation noise as a result of the minimal change in accommodative response. In the mid-aged subjects (35-44 years of age), the apparent increase in AC/Ar with age was speculated to be due to neural adaptation of the crosslink gain from the accommodative to the vergence system and/or slight intrusion into the upper non-linear response region of accommodation with the measurements. The finding of AC/Ar constancy with age when mid-aged pre-presbyopes and early presbyopes were excluded supports the non-linearity hypothesis, and thus there appears to be no real change in AC/Ar with increased age. The results support the Hess-Gullstrand theory of presbyopia.

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The AC/A Ratio and Age—A Longitudinal Study

Cited by 14 publications

References 0 publications

The eye in focus: accommodation and presbyopia

The eye in focus: accommodation and presbyopia

The effect of incipient presbyopia on the correspondence between accommodation and vergence

The AC/A ratio, age and presbyopia

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