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Gordon Heron, W. Neil Charman, Lyle S. Gray; Accommodation Responses and Ageing. Invest. Ophthalmol. Vis. Sci. 1999;40(12):2872-2883.
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purpose. To study the impact of age on accommodation dynamics.
methods. Monocular accommodation responses were measured continuously using a
modified Canon Auto Ref R1 infrared optometer. The stimulus was a
single letter oscillating sinusoidally between 2.38 and 1.33 D
providing a stimulus amplitude of 0.52 D, about a mean level of 1.86 D.
Response characteristics were used to quantify gain and phase. Step
responses were also recorded between these stimulus vergence levels for
calibration purposes and to measure reaction and response times.
Nineteen visually normal subjects 18 to 49 years of age participated,
and 11 frequencies were used in the range 0.05 to 1.0 Hz. A key feature
of the experimental design was to use a stimulus vergence range that
lay within the amplitude of accommodation of all the observers.
results. Accommodation gain reduced and phase lag increased with age,
particularly at the higher frequencies used. No strongly significant
change with age was found for reaction and response times or
accommodation velocity, and results were similar for both far-to-near
and near-to-far responses. Response amplitude for the step change in
target vergence declined with age, and substantial differences were
found between the measured and predicted (from reaction time) phase
lags at 1.0 Hz as a function of age. Young observers showed a phase lag
that was shorter than predicted, whereas older observers’ measured
phase lags were considerably larger than predicted.
conclusions. Results show that for a target oscillating sinusoidally in a
predictable manner at a modest amplitude, the main ageing effects occur
in phase lag, which is appreciably longer than predicted from reaction
times in the older observers. The effects of ageing on gain were not as
marked. Although responses to small step changes do reduce with age,
there is no evidence of increased response times with ageing. In
general, accommodation function in the middle-aged eye is quite robust
despite a dwindling amplitude of accommodation. These results provide
evidence of accommodative vigor in youth and a slowing of accommodation
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