| Spatial contrast sensitivity at twilight: luminance, monocularity, and oxygenation. | |
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MedLine Citation:
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PMID: 20464814 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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INTRODUCTION: Visual performance in dim light is compromised by lack of oxygen (hypoxia). The possible influence of altered oxygenation on foveal contrast sensitivity under mesopic (twilight) viewing conditions is relevant to aircrew flying at night, including when using night vision devices, but is poorly documented. METHODS: Foveal contrast sensitivity was measured binocularly and monocularly in 12 subjects at 7 spatial frequencies, ranging from 0.5 to approximately 16 cycles per degree, using sinusoidal Gabor patch gratings. Hypoxic performance breathing 14.1% oxygen, equivalent to altitude exposure at 3048 m (10,000 ft), was compared with breathing air at sea level (normoxia) at low photopic (28 cd x m(-2)), borderline upper mesopic (approximately 2.1 cd x m(-2)) and midmesopic (approximately 0.26 cd x m(-2)) luminance. Mesopic performance was also assessed breathing 100% oxygen (hyperoxia). RESULTS: Typical 'inverted U' log/log plots of the contrast sensitivity function were obtained, with elevated thresholds (reduced sensitivity) at lower luminance. Binocular viewing enhanced sensitivity by a factor approximating square root of 2 for most conditions, supporting neural summation of the contrast signal, but had greater influence at the lowest light level and highest spatial frequencies (8.26 and 16.51 cpd). Respiratory challenges had no effect. CONCLUSIONS: Contrast sensitivity is poorer when viewing monocularly and especially at midmesopic luminance, with relevance to night flying. The foveal contrast sensitivity function is unaffected by respiratory disturbance when twilight conditions favor cone vision, despite known effects on retinal illumination (pupil size). The resilience of the contrast sensitivity function belies the vulnerability of foveal low contrast acuity to mild hypoxia at mesopic luminance. |
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Authors:
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Desmond M Connolly |
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Publication Detail:
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Type: Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Aviation, space, and environmental medicine Volume: 81 ISSN: 0095-6562 ISO Abbreviation: Aviat Space Environ Med Publication Date: 2010 May |
Date Detail:
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Created Date: 2010-05-14 Completed Date: 2010-06-08 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 7501714 Medline TA: Aviat Space Environ Med Country: United States |
Other Details:
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Languages: eng Pagination: 475-83 Citation Subset: IM; S |
Affiliation:
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Human Protection and Performance Enhancement Group, QinetiQ PLC, Cody Technology Park, Bldg. A54, Ively Road, Farnborough, Hampshire GU14 0LX, UK. dmconnolly@qinetiq.com |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adult Aerospace Medicine Analysis of Variance Anoxia / physiopathology* Contrast Sensitivity* Female Humans Male Mesopic Vision* Sex Characteristics Vision, Monocular |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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