Document Detail


Role of ocular aberrations in dynamic accommodation control.
MedLine Citation:
PMID:  19462504     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
BACKGROUND: Accommodation control is mediated by a number of cues, including blur,chromatic aberration and target proximity. Data from wavefront measurements have shown clear shifts in ocular aberrations during increasing accommodative demand, most notably a negative shift in spherical aberration. Work in adaptive optics, where aberrations have been corrected, has suggested a role for aberrations in the control of accommodation for some individuals. This study aimed to determine the relative effects of aberration correction and inversion on closed-loop stepwise accommodation responses to small increases and decreases in stimulus vergence. METHODS: An adaptive optics system was used to modify ocular aberrations, while five participants viewed a high contrast target stepping 0.5 D in an inward or outward direction. Aberrations were variously unchanged, corrected or inverted following the step change in stimulus vergence. A Shack-Hartmann wavefront sensor was used to record accommodative responses to the stepwise changes in stimulus vergence. Accommodative response data were analysed using a curve fitting method to calculate the gain,latency and response time. RESULTS: Correction of aberrations failed to have a significant effect on dynamic accommodative responses. Inversion of even-order aberration terms produced a significant reduction in accommodative response gain for outward steps in stimulus vergence.Additionally, an increase in the number of accommodative responses in the wrong direction was seen following aberration inversion. Inward steps were not altered significantly by aberration inversion. CONCLUSION: Accommodation in humans appears to derive a cue from the even-order aberrations of the eye to help guide the initial direction of responses to reductions in stimulus vergence (that is, disaccommodation). With all aberrations and even-order aberrations inverted, the number of incorrect directional responses to outward moving stimuli increases, suggesting that aberrations are important in determining the initial path of stepwise accommodative responses.
Authors:
Sem Sem Chin; Karen M Hampson; Edward A H Mallen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Clinical & experimental optometry : journal of the Australian Optometrical Association     Volume:  92     ISSN:  1444-0938     ISO Abbreviation:  Clin Exp Optom     Publication Date:  2009 May 
Date Detail:
Created Date:  2009-05-21     Completed Date:  2009-07-30     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8703442     Medline TA:  Clin Exp Optom     Country:  Australia    
Other Details:
Languages:  eng     Pagination:  227-37     Citation Subset:  IM    
Affiliation:
Bradford School of Optometry and Vision Science, University of Bradford, Bradford, West Yorkshire, United Kingdom.
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MeSH Terms
Descriptor/Qualifier:
Accommodation, Ocular / physiology*
Adaptation, Physiological / physiology*
Adult
Astigmatism / diagnosis,  physiopathology*
Cornea / physiology
Corneal Topography
Female
Humans
Male
Photic Stimulation
Reaction Time / physiology
Visual Acuity / physiology*
Young Adult

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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