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Accommodative amplitude required for sustained near work
Author(s) -
Wolffsohn James S,
Sheppard Amy L,
Vakani Sanjay,
Davies Leon N
Publication year - 2011
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1111/j.1475-1313.2011.00847.x
Subject(s) - accommodation , autorefractor , optometry , presbyopia , binocular vision , psychology , heterophoria , near vision , visual acuity , audiology , medicine , computer science , ophthalmology , refractive error , strabismus , computer vision , neuroscience
Citation information : Wolffsohn JS, Sheppard AL, Vakani S & Davies LN. Accommodative amplitude required for sustained near work. Ophthalmic Physiol Opt 2011, 31 , 480–486. doi: 10.1111/j.1475‐1313.2011.00847.x Abstract 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.