| Subjective fixation disparity affected by dynamic asymmetry, resting vergence, and nonius bias. | |
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MedLine Citation:
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PMID: 21467184 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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PURPOSE. We investigate how subjectively measured fixation disparity can be explained by (1) the convergent-divergent asymmetry of vergence dynamics (called dynamic asymmetry) for a disparity vergence step stimulus of 1 degree (60 min arc), (2) the dark vergence, and (3) the nonius bias. METHODS. Fixation disparity, dark vergence, and nonius bias were measured subjectively using nonius lines at a 60-cm viewing distance. Dynamic vergence step responses (both convergent and divergent) were measured objectively with the EyeLink II. RESULTS. In 20 subjects (mean age 24.5 ± 4.3 years, visual acuity ≥1.0, all emmetropic except for one with myopia, wearing contact lenses), multiple regression analyses showed that 39% of the variance in subjective fixation disparity was due to the characteristic factors of physiological vergence: dynamic asymmetry (calculated from convergent and divergent velocities) and dark vergence. An additional 23% of variance was due to the subjective nonius bias, i.e., the physical nonius offset required for perceived alignment of binocularly (non-dichoptically) presented nonius lines. Together, these factors explained 62% of the inter-individual differences in subjectively measured fixation disparity, demonstrating the influence of oculomotor and perceptual factors. CONCLUSIONS. The clinically relevant subjective fixation disparity originates from distinct physiological sources: dynamic asymmetry in vergence dynamics, resting vergence and nonius bias were found to affect fixation disparity directly, not only via changes in vergence dynamics. |
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Authors:
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Aiga Svede; Jörg Hoormann; Stephanie Jainta; Wolfgang Jaschinski |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-4-5 |
Journal Detail:
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Title: Investigative ophthalmology & visual science Volume: - ISSN: 1552-5783 ISO Abbreviation: - Publication Date: 2011 Apr |
Date Detail:
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Created Date: 2011-4-6 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 7703701 Medline TA: Invest Ophthalmol Vis Sci Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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Department of Optometry and Vision Science, University of Latvia, Riga, Latvia. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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