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Article: Relationship between visual span and reading performance in age-related macular degeneration

TitleRelationship between visual span and reading performance in age-related macular degeneration
Authors
KeywordsAge-related macular degeneration
Information transfer rate
Letter recognition
Low vision
Reading speed
Visual span
Issue Date2008
PublisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/visres
Citation
Vision Research, 2008, v. 48 n. 4, p. 577-588 How to Cite?
AbstractPurpose: Visual-span profiles are plots of letter-recognition accuracy as a function of letter position left and right of the point of fixation. Legge, Mansfield, and Chung [Legge, G. E., Mansfield, J. S., & Chung, S. T. L. (2001). Psychophysics of reading-XX. Linking letter recognition to reading speed in central and peripheral vision. Vision Research, 41(6), 725-743] proposed that reduced size of the visual span is a spatial factor limiting reading speed in patients with age-related macular degeneration (AMD). We have recently shown that a temporal property of letter recognition-the exposure time required for a high level of accuracy-is also a factor limiting reading speed in AMD [Cheong, A. M. Y., Legge, G. E., Lawrence, M. G., Cheung, S. H., & Ruff, M. (2007). Relationship between slow visual processing and reading speed in people with macular degeneration. Vision Research, 47, 2943-2965]. We measured the visual-span profiles of AMD subjects and assessed the relationship of the spatial and temporal properties of these profiles to reading speed. Methods: Thirteen AMD subjects and 11 age-matched normals were tested. Visual-span profiles were measured by using the trigram letter-recognition method described by Legge et al. (2001). Each individual's temporal threshold for letter recognition (80% accuracy criterion) was used as the exposure time for measuring the visual-span profile. Size of the visual span was computed as the area under the profile in bits of information transmitted. The information transfer rate in bits per second was defined as the visual-span size in bits divided by the exposure time in sec. Results: AMD visual-span sizes were substantially smaller (median of 23.9 bits) than normal visual-span sizes in central vision (median of 40.8 bits, p < .01). For the nine AMD subjects with eccentric fixation, the visual-span sizes (median of 20.6 bits) were also significantly smaller than visual spans of normal controls at 10° below fixation in peripheral vision (median of 29.0 bits, p = .01). Information transfer rate for the AMD subjects (median of 29.5 bits/s) was significantly slower than that for the age-matched normals at both central and peripheral vision (median of 411.7 and 290.5 bits/s respectively, ps < .01). Information transfer rates were more strongly correlated with reading speed than the size of the visual span, and explained 36% of the variance in AMD reading speed. Conclusion: Both visual-span size and information transfer rate were significantly impaired in the AMD subjects compared with age-matched normals. Information transfer rate, representing the combined effects of a reduced visual span and slower temporal processing of letters, was a better predictor of reading speed in AMD subjects than was the size of the visual span. © 2007 Elsevier Ltd. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/89434
ISSN
2015 Impact Factor: 1.776
2015 SCImago Journal Rankings: 0.957
PubMed Central ID
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorCheong, AMYen_HK
dc.contributor.authorLegge, GEen_HK
dc.contributor.authorLawrence, MGen_HK
dc.contributor.authorCheung, SHen_HK
dc.contributor.authorRuff, MAen_HK
dc.date.accessioned2010-09-06T09:56:58Z-
dc.date.available2010-09-06T09:56:58Z-
dc.date.issued2008en_HK
dc.identifier.citationVision Research, 2008, v. 48 n. 4, p. 577-588en_HK
dc.identifier.issn0042-6989en_HK
dc.identifier.urihttp://hdl.handle.net/10722/89434-
dc.description.abstractPurpose: Visual-span profiles are plots of letter-recognition accuracy as a function of letter position left and right of the point of fixation. Legge, Mansfield, and Chung [Legge, G. E., Mansfield, J. S., & Chung, S. T. L. (2001). Psychophysics of reading-XX. Linking letter recognition to reading speed in central and peripheral vision. Vision Research, 41(6), 725-743] proposed that reduced size of the visual span is a spatial factor limiting reading speed in patients with age-related macular degeneration (AMD). We have recently shown that a temporal property of letter recognition-the exposure time required for a high level of accuracy-is also a factor limiting reading speed in AMD [Cheong, A. M. Y., Legge, G. E., Lawrence, M. G., Cheung, S. H., & Ruff, M. (2007). Relationship between slow visual processing and reading speed in people with macular degeneration. Vision Research, 47, 2943-2965]. We measured the visual-span profiles of AMD subjects and assessed the relationship of the spatial and temporal properties of these profiles to reading speed. Methods: Thirteen AMD subjects and 11 age-matched normals were tested. Visual-span profiles were measured by using the trigram letter-recognition method described by Legge et al. (2001). Each individual's temporal threshold for letter recognition (80% accuracy criterion) was used as the exposure time for measuring the visual-span profile. Size of the visual span was computed as the area under the profile in bits of information transmitted. The information transfer rate in bits per second was defined as the visual-span size in bits divided by the exposure time in sec. Results: AMD visual-span sizes were substantially smaller (median of 23.9 bits) than normal visual-span sizes in central vision (median of 40.8 bits, p < .01). For the nine AMD subjects with eccentric fixation, the visual-span sizes (median of 20.6 bits) were also significantly smaller than visual spans of normal controls at 10° below fixation in peripheral vision (median of 29.0 bits, p = .01). Information transfer rate for the AMD subjects (median of 29.5 bits/s) was significantly slower than that for the age-matched normals at both central and peripheral vision (median of 411.7 and 290.5 bits/s respectively, ps < .01). Information transfer rates were more strongly correlated with reading speed than the size of the visual span, and explained 36% of the variance in AMD reading speed. Conclusion: Both visual-span size and information transfer rate were significantly impaired in the AMD subjects compared with age-matched normals. Information transfer rate, representing the combined effects of a reduced visual span and slower temporal processing of letters, was a better predictor of reading speed in AMD subjects than was the size of the visual span. © 2007 Elsevier Ltd. All rights reserved.en_HK
dc.languageengen_HK
dc.publisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/visresen_HK
dc.relation.ispartofVision Researchen_HK
dc.subjectAge-related macular degenerationen_HK
dc.subjectInformation transfer rateen_HK
dc.subjectLetter recognitionen_HK
dc.subjectLow visionen_HK
dc.subjectReading speeden_HK
dc.subjectVisual spanen_HK
dc.titleRelationship between visual span and reading performance in age-related macular degenerationen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0042-6989&volume=48&issue=4&spage=577&epage=588&date=2008&atitle=Relationship+between+visual+span+and+reading+performance+in+age-related+macular+degenerationen_HK
dc.identifier.emailCheung, SH:singhang@hku.hken_HK
dc.identifier.authorityCheung, SH=rp00590en_HK
dc.description.naturelink_to_OA_fulltext-
dc.identifier.doi10.1016/j.visres.2007.11.022en_HK
dc.identifier.pmid18191983-
dc.identifier.pmcidPMC2323914-
dc.identifier.scopuseid_2-s2.0-38749094080en_HK
dc.identifier.hkuros140634en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-38749094080&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume48en_HK
dc.identifier.issue4en_HK
dc.identifier.spage577en_HK
dc.identifier.epage588en_HK
dc.identifier.isiWOS:000253786400006-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridCheong, AMY=7003847650en_HK
dc.identifier.scopusauthoridLegge, GE=7005064208en_HK
dc.identifier.scopusauthoridLawrence, MG=8410649400en_HK
dc.identifier.scopusauthoridCheung, SH=7202473508en_HK
dc.identifier.scopusauthoridRuff, MA=22235672200en_HK
dc.identifier.citeulike3500734-

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