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The relationship between stimulus intensity and response amplitude for the photopic negative response of the flash electroretinogram.
MedLine Citation:
PMID:  21243403     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The aim of this study was to investigate the relationship between stimulus intensity and response amplitude for the photopic negative response (PhNR) of the flash ERG. Specific aims were (i) to determine whether a generalized Naka-Rushton function provided a good fit to the intensity-response data and (ii) to determine the variability of the parameters of the best-fitting Naka-Rushton models. Electroretinograms were recorded in 18 participants, on two occasions, using both DTL fibre and skin active electrodes, in response to Ganzfeld red stimuli (Lee filter "terry red") ranging in stimulus strength from -1.30 to 0.53 log cd.s.m(-2) (0.28-2.11 log phot td.s) presented over a steady blue background (Schott glass filter BG28; 3.9 log scot td). PhNR amplitude was measured from b-wave peak and from pre-stimulus baseline. The Naka-Rushton function was fitted to all intensity-response data, and parameters, 'n', 'Vmax' and 'K' were obtained. Coefficients of variation (CoV), and inter-ocular and inter-session limits of agreement (LoA) were calculated for both Naka-Rushton parameters. A generalized Naka-Rushton function was found to provide a good fit to the intensity-response data, except at the highest stimulus intensity, where a reduction in amplitude occurred in many individuals. The 'Vmax' parameter was less variable than 'K' for all intensity-response data. Variability was lower for DTL than skin electrodes, and for peak-to-trough PhNR measurements, compared to baseline-to-trough. This study has demonstrated for the first time that the Naka-Rushton model provides a useful means of quantifying the intensity-response relationship of the PhNR.
Authors:
A M Binns; K E Mortlock; R V North
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-1-18
Journal Detail:
Title:  Documenta ophthalmologica. Advances in ophthalmology     Volume:  -     ISSN:  1573-2622     ISO Abbreviation:  -     Publication Date:  2011 Jan 
Date Detail:
Created Date:  2011-1-18     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370667     Medline TA:  Doc Ophthalmol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, CF24 4LU, UK, BinnsAM@cf.ac.uk.
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