ORIGINAL RESEARCH ARTICLE Spectral characteristics of the PhNR in the full-ﬁeld ﬂash electroretinogram of normals and glaucoma patients Jan Kremers • Mounira Jertila • Barbara Link • Gobinda Pangeni • Folkert K. Horn Received: 2 August 2011 / Accepted: 12 December 2011 / Published online: 8 January 2012 Ó Springer-Verlag 2012 Abstract Flash electroretinogram responses were measured in normal subjects to different chromatic combinations of ﬂashes and backgrounds. The ampli- tudes of the ﬂash response components were measured at different ﬂash strengths and could be described by a generalized Naka-Rushton function. The measure- ments were repeated at different background lumi- nances to study adaptation effects. It was found that when ﬂash strength and background luminance were expressed in photometric terms (cd s/m 2 and cd/m 2 , respectively), then the responses were very similar for all chromatic combinations with the exception of the condition in which blue (peak wavelength 458 nm) was ﬂashed upon an orange (peak wave- length 591 nm) background. We propose that in this condition, a second (possibly S-cone or rod-driven) mechanism intrudes. The negative response after the b-wave (here called ‘‘photopic negative response’’ or PhNR for all conditions) is thought to reﬂect ganglion cell activity and was also largest at this condition. Responses were measured to the 458 nm ﬂash on 591 nm background and the reversed combination in a population of 39 normal subjects and 49 glaucoma patients. It was found that the PhNR amplitude was affected by glaucoma in all conditions. Other compo- nent parameters, reﬂecting responses and adaptation dynamics, were not altered. The best stimulus condi- tion among the conditions used to separate the PhNR amplitude of normals and patients was a 1 cd s/m 2 458 nm ﬂash on a 10 cd/m 2 591 nm background. Keywords Electroretinogram  Spectral composition  Flash stimuli  Photopic negative response Introduction The electroretinogram (ERG) is an electrical potential that originates in the retina. Activities of several different retinal cell types contribute to the ERG response. In the ﬂash ERG, different components can be distinguished, each of which originate through activity in a distinct cell type. The a- and b-wave are well-known components and can be attributed mainly to activity in the photoreceptors and bipolar cells [1]. The photopic negative response (PhNR) of the phot- opic ﬂash ERG has been shown to reﬂect spiking activity of the retinal ganglion cells. This ﬁnding is important because the PhNR may be used as a tool to diagnose and monitor disorders of the inner retina, J. Kremers (&)  M. Jertila  B. Link  G. Pangeni  F. K. Horn Department of Ophthalmology, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany e-mail: jan.kremers@uk-erlangen.de M. Jertila Klinik und Poliklinik fu ¨r Augenheilkunde, Klinikum rechts der Isar, Technical University Munich, Ismaninger Str. 22, 81675 Munich, Germany 123 Doc Ophthalmol (2012) 124:79–90 DOI 10.1007/s10633-011-9304-z