Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists) · 2011
Accommodative amplitude required for sustained near work.
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Wolffsohn James S, Sheppard Amy L, Vakani Sanjay, Davies Leon N
Аннотация
PURPOSE: Many practitioners base the prescription of near vision additions on the assertion that only one half or two-thirds of an individual's amplitude of accommodation is sustainable for a prolonged period. To better understand how much eye focus needs to be restored for presbyopic corrections to be adequate, this study investigated the robustness of the pre-presbyopic human accommodative system during a sustained and intensive near vision task.
METHODS: Twenty-one pre-presbyopic volunteers (aged 26.1 ± 4.7 years) participated in the study. Binocular subjective amplitude of accommodation was measured before and after a prolonged reading exercise, using the RAF rule. During the 30 min reading task, the subject's closest comfortable eye-to-text distance and pupil size was monitored. Accommodative accuracy to 0.2, 1.0, 2.0, 3.0 and 4.0 D stimuli was determined objectively using a validated binocular open-view autorefractor immediately before, and after the reading task.
RESULTS: Amplitude of accommodation (p=0.09) and accommodative accuracy (p>0.05) were statistically unchanged following the intensive near task. The mean proportion of accommodation exerted throughout the near exercise was 80.6% (range 45.3 ± 3.7 to 96.6 ± 4.3%), which increased as the task progressed (F=2.24, p=0.02). The mean percentage of accommodation utilised increased with subject age (r=0.517, p = 0.016).
CONCLUSION: The pre-presbyopic human accommodative system is robust to fatigue during intense and prolonged near work. A greater proportion of one's amplitude of accommodation may be continuously exerted than previously suggested.
METHODS: Twenty-one pre-presbyopic volunteers (aged 26.1 ± 4.7 years) participated in the study. Binocular subjective amplitude of accommodation was measured before and after a prolonged reading exercise, using the RAF rule. During the 30 min reading task, the subject's closest comfortable eye-to-text distance and pupil size was monitored. Accommodative accuracy to 0.2, 1.0, 2.0, 3.0 and 4.0 D stimuli was determined objectively using a validated binocular open-view autorefractor immediately before, and after the reading task.
RESULTS: Amplitude of accommodation (p=0.09) and accommodative accuracy (p>0.05) were statistically unchanged following the intensive near task. The mean proportion of accommodation exerted throughout the near exercise was 80.6% (range 45.3 ± 3.7 to 96.6 ± 4.3%), which increased as the task progressed (F=2.24, p=0.02). The mean percentage of accommodation utilised increased with subject age (r=0.517, p = 0.016).
CONCLUSION: The pre-presbyopic human accommodative system is robust to fatigue during intense and prolonged near work. A greater proportion of one's amplitude of accommodation may be continuously exerted than previously suggested.