Document Detail


Rapid method for assessing rod function using recovery of spatial contrast thresholds following a bleach.
MedLine Citation:
PMID:  25016055     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Poor vision in low light is a common complaint of elderly people. This poorly understood phenomenon is likely to involve both receptoral and post receptoral mechanisms. We investigated the recovery of contrast thresholds for sine-wave gratings of low spatial frequencies and low mean luminance as a function of time in darkness after photo pigment bleaching. Thirteen subjects aged 30.4(±10.7) years took part in the study. Contrast thresholds were measured for 15 minutes following almost complete photo pigment bleaching. The stimuli were achromatic sinusoidal gratings of 0.5, 1 and 2 cycle per degree (cpd) generated on a CRT monitor. They had mean luminance 0.01 cd.m(-2) and subtended 10° in diameter. The dynamics of the recovery at each spatial frequency were modelled using monophasic and biphasic exponential decay functions. The data were best modelled by a bi-phasic decay with a distinct transition point around 7 min after the bleach. Both phases followed an exponential decay. The time constant (mean, standard error) for the first phase was 0.35 (0.04) minutes while for the second phase it was 5.15 (0.27) minutes. This difference was statistically significant (p<0.001). A control experiment revealed the second, slower phase was mediated by rod photoreceptors. Maximum contrast sensitivity was reached 15 minutes after a photic bleach. The dynamics of contrast sensitivity recovery follow two phases and these may be attributed to the cone and rod systems.
Authors:
M Cinta Puell; Jeremiah Mf Kelly; Ian J Murray
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-7-9
Journal Detail:
Title:  Experimental eye research     Volume:  -     ISSN:  1096-0007     ISO Abbreviation:  Exp. Eye Res.     Publication Date:  2014 Jul 
Date Detail:
Created Date:  2014-7-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370707     Medline TA:  Exp Eye Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2014. Published by Elsevier Ltd.
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