Inter-ocular and inter-session reliability of the electroretinogram photopic negative response (PhNR) in non-human primates
Introduction
The flash electroretinogram (ERG) is frequently used for assessment of retinal function in both clinical and laboratory settings. As with any such test, its inter-session reliability determines the confidence with which the effects of a clinical disease, disease model, or therapeutic intervention can be distinguished from inherent measurement variability. To date, few studies of full-field ERG test–retest reliability appear in the literature; and to our knowledge, none for non-human primates. Given the extensive use of non-human primates in ophthalmic research, the inter-session reliability of the full-field ERG should be quantified.
Although well established as a measure of photoreceptor and bipolar cell activity, the full-field flash ERG was thought to contain little, if any contribution from ganglion cells. Thus, its application to basic and clinical studies of glaucoma, or other diseases of the optic nerve, has been relatively limited (Vaegan et al., 1991, Korth, 1997, Graham and Klistorner, 1998, Holopigian et al., 2000, Bach, 2001). More recently, studies by Frishman and colleagues have demonstrated that slow negative components in the flash ERG response, measured under both dark-adapted (scotopic), and light-adapted (photopic) conditions are dependent on ganglion cell activity and are reduced in experimental and human glaucoma (Frishman et al., 1996a, Frishman et al., 1996b, Viswanathan et al., 1999, Frishman et al., 2000, Viswanathan et al., 2000). This has led to renewed interest in the use of the full-field ERG for detection of abnormal function in human glaucoma and experimental models of glaucoma (Frishman et al., 1996a, Frishman et al., 1996b, Colotto et al., 2000, Cursiefen et al., 2001, Drasdo et al., 2001, Viswanathan et al., 2001).
The slow negative potential recorded in the scotopic flash response is relatively small and only observed near ERG threshold (Sieving et al., 1986, Naarendorp et al., 2001). Thus named the scotopic threshold response (STR), its measurement requires sufficient dark-adaptation and extensive signal averaging. Furthermore, some controversy exists regarding the extent to which the STR is affected by ganglion cell loss in humans (Sieving, 1991, Korth et al., 1994). In contrast, an analogous slow negative potential that follows the b-wave of the photopic ERG (called the photopic negative response or ‘PhNR’) is substantially larger and easier to record. Perhaps not surprisingly then, the PhNR has been used by several other investigators in studies of human glaucoma (Colotto et al., 2000, Cursiefen et al., 2001, Drasdo et al., 2001).
Given that the PhNR may be of use in human and experimental glaucoma, it is important to establish its reliability, especially for longitudinal studies of disease progression and/or therapeutic intervention. The purpose of this study was to compare inter-ocular and inter-session reliability of the PhNR with other components of the photopic ERG in a group of normal macaque monkeys. In addition, changes in the PhNR were compared with changes in other photopic ERG parameters following pharmacologic suppression of inner-retinal light responses.
Section snippets
Experimental animals
All experimental methods and animal care procedures adhered to the Association for Research in Vision and Ophthalmology's Statement for the Use of Animals in Ophthalmic and Vision Research and were approved by the local Institutional Animal Care and Use Committee (IACUC). Inter-ocular variability was assessed in 29 adult female rhesus monkeys (Macaca mulatta) ranging in age from 9 to 14 years, whereas inter-session reproducibility was considered for 23 eyes of 23 animals (all left eyes)
Results
Examples of photopic ERG responses to four stimulus intensities are presented in Fig. 1. For all flash intensities the photopic ERG response of the monkey recorded under these conditions had the characteristic a-wave and b-wave complex. OPs were found superimposed on the rising slope of the positive b-wave, while the late, negative PhNR followed the b-wave. Note that waveform morphology changed between 0·42 and 0·67 such that the b-wave became smaller and the PhNR implicit time abruptly shifted
Discussion
The photopic ERG waveforms measured in this study were similar to those previously reported for primates using short-duration, red full-field flashes across a range of stimulus intensities (Viswanathan et al., 1999). The results of this study show that while OP and a-wave amplitudes increased along a typical saturating function with stimulus intensity, the amplitude of the PhNR actually began to decline above 0·42 log cd.s m−2 much like that observed for the b-wave. This observation suggests
Acknowledgements
The authors wish to thank Karin Novitsky for her assistance with data collection. This study was supported in part by grants from the National Institutes of Health EY05231 (G.A.C.), M.J. Murdock Charitable Trust, Vancouver, WA, USA, and Allergan, Inc., Irvine, CA, USA.
References (42)
- et al.
Yearly rates of rod and cone functional loss in retinitis pigmentosa and cone-rod dystrophy
Ophthalmology
(1999) - et al.
Baseline characteristics of the transient pattern electroretinogram in non-human primates: inter-ocular and inter-session variability
Exp. Eye Res.
(2003) - et al.
Visual field defects and neural losses from experimental glaucoma
Prog. Retin. Eye Res.
(2002) - et al.
The photopic ERG luminance-response function (photopic hill): method of analysis and clinical application
Vis. Res.
(2003) Analysis of the rabbit's electroretinogram following unilateral transection of the optic nerve
Exp. Eye Res.
(1972)Electrophysiological approaches for early detection of glaucoma
Eur. J. Ophthalmol.
(2001)- et al.
The intrasession repeatability of pattern electroretinograms and the effects of digital filtering
Doc. Ophthalmol.
(1991) - et al.
Comparisons of the amplitude size and the reproducibility of three different electrodes to record the corneal flash electroretinogram in rodents
Doc. Ophthalmol.
(1999) - et al.
Quantitative electroretinogram measures of phototransduction in cone and rod photoreceptors: normal aging, progression with disease, and test–retest variability
Arch. Ophthalmol.
(2002) - et al.
Statistical methods for assessing agreement between two methods of clinical measurements
Lancet.
(1986)
Effect of spike blockade on the receptive-field size of amacrine and ganglion cells in the rabbit retina
J. Neurophysiol.
Voltage- and transmitter-gated currents of all-amacrine cells in a slice preparation of the rat retina
J. Neurosci.
Comparison of guinea pig electroretinograms measured with bipolar corneal and unipolar intravitreal electrodes
Doc. Ophthalmol.
Photopic negative response of the human ERG: losses associated with glaucomatous damage
Invest. Ophthalmol. Vis. Sci.
The negative response of the flash electroretinogram in glaucoma
Doc. Ophthalmol.
The s-cone PHNR and pattern ERG in primary open angle glaucoma
Invest. Ophthalmol. Vis. Sci.
Effects of background light on the human dark-adapted electroretinogram and psychophysical threshold
J. Opt. Soc. Am. A.
Effects of experimental glaucoma in macaques on the multifocal ERG. Multifocal ERG in laser-induced glaucoma
Doc. Ophthalmol.
The scotopic electroretinogram of macaque after retinal ganglion cell loss from experimental glaucoma
Invest. Ophthalmol. Vis. Sci.
Comparison of psychophysical and electrophysiological testing in early glaucoma
Invest. Ophthalmol. Vis. Sci.
Electrophysiology: a review of signal origins and applications to investigating glaucoma
Aust. N. Z. J. Ophthalmol.
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