Document Detail

Asymmetrical growth of the photopic hill during the light adaptation effect.
MedLine Citation:
PMID:  20711798     Owner:  NLM     Status:  In-Process    
In response to progressively stronger flashes delivered against a rod saturating background light, the amplitude of the photopic ERG b-wave first increases, reaches a maximal value (V (max)) and then decreases gradually to a plateau where the amplitude of the b-wave equals that of the a-wave, a phenomenon known as the photopic hill (PH). The purpose of this study was to investigate how the PH grew during the course of the light adaptation (LA) process that follows a period of dark adaptation (DA): the so-called light adaptation effect (LAE). Photopic ERG (time-integrated) luminance-response (LR) functions were obtained prior to (control-fully light adapted) and at 0, 5 and 10 min of LA following a 30-min period of DA. A mathematical model combining a Gaussian and a logistic growth function, suggested to reflect the OFF and ON retinal contribution to the PH respectively, was fitted to the LR functions thus obtained. Our results indicate that the magnitude of the cone ERG LAE is modulated by the stimulus luminance, with b-wave enhancements being maximal for luminance levels that result in the descent of the PH. The Gaussian function grew significantly with LA while the logistic growth function remained basically unchanged. Our findings would therefore suggest that the LAE reflects primarily an increase in the retinal OFF response during LA.
Marie-Lou Garon; Marianne Rufiange; Ruth Hamilton; Daphne L McCulloch; Pierre Lachapelle
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-08-15
Journal Detail:
Title:  Documenta ophthalmologica. Advances in ophthalmology     Volume:  121     ISSN:  1573-2622     ISO Abbreviation:  Doc Ophthalmol     Publication Date:  2010 Dec 
Date Detail:
Created Date:  2010-11-03     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370667     Medline TA:  Doc Ophthalmol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  177-87     Citation Subset:  IM    
Department of Ophthalmology and Neurology-Neurosurgery, Montreal Children's Hospital Research Institute, McGill University, 2300 Tupper Street, Montréal, QC, H3H 1P3, Canada.
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