Photopic Negative Response Of Electroretinogram Research Articles

Multifocal Electroretinogram Photopic Negative Response: A Reliable Paradigm to Detect Localized Retinal Ganglion Cells' Impairment in Retrobulbar Optic Neuritis Due to Multiple Sclerosis as a Model of Retinal Neurodegeneration.

The measure of the full-field photopic negative response (ff-PhNR) of light-adapted full-field electroretinogram (ff-ERG) allows to evaluate the function of the innermost retinal layers (IRL) containing primarily retinal ganglion cells (RGCs) and other non-neuronal elements of the entire retina. The aim of this study was to acquire functional information of localized IRL by measuring the PhNR in response to multifocal stimuli (mfPhNR). In this case-control observational and retrospective study, we assessed mfPhNR responses from 25 healthy controls and from 20 patients with multiple sclerosis with previous history of optic neuritis (MS-ON), with full recovery of visual acuity, IRL morphological impairment, and absence of morpho-functional involvement of outer retinal layers (ORL). MfPhNR response amplitude densities (RADs) were measured from concentric rings (R) with increasing foveal eccentricity: 0–5° (R1), 5–10° (R2), 10–15° (R3), 15–20° (R4), and 20–25° (R5) from retinal sectors (superior-temporal (ST), superior-nasal (SN), inferior-nasal (IN), and inferior-temporal (IT)); between 5° and 20° and from retinal sectors (superior (S), temporal (T), inferior (I), and nasal (N)); and within 5° to 10° and within 10° and 20° from the fovea. The mfPhNR RAD values observed in all rings or sectors in MS-ON eyes were significantly reduced (p < 0.01) with respect to control ones. Our results suggest that mfPhNR recordings may detect localized IRL dysfunction in the pathologic condition of selective RGCs neurodegeneration.

Comparison of photopic negative response of electroretinogram in non-diabetic and diabetic indian subjects

Comparison of photopic negative response of electroretinogram in non-diabetic and diabetic indian subjects

Exploratory Study of the Association between the Severity of Idiopathic Intracranial Hypertension and Electroretinogram Photopic Negative Response Amplitude Obtained Using a Handheld Device.

The photopic negative response (PhNR) is a negative component of the photopic flash electroretinogram that follows the b-wave and is thought to arise from the retinal ganglion cells. Reduction in its amplitude in idiopathic intracranial hypertension (IIH) has been previously documented using formal electroretinography. This study explored the use of a handheld device (RETeval, LKC technologies, Gaithersburg, MD, USA) in 72 IIH patients of varying stages and severity (and seven controls) and investigated associations between PhNR parameters and disease severity. PhNR amplitudes at 72 ms (P72) and p-ratio (ratio to b-wave peak value) differed significantly across groups, with a trend towards smaller amplitudes in those with severe IIH, defined as papilloedema with Modified Frisén Scale (MFS) ≥ 3, retinal nerve fibre layer (RNFL) ≥ 150 μm or atrophic papilloedema (p = 0.0048 and p = 0.018 for P72 and p-ratio, respectively). PhNR parameters did not correlate with MFS, RNFL thickness, standard automated perimetry mean deviation or macular ganglion cell layer volume. This study suggests that PhNR measurement using a handheld device is feasible and could potentially augment the assessment of disease severity in IIH. The clinical utility of PhNR monitoring in IIH patients requires further investigation.

Advanced progress of the electroretinogram photopic negative response

The photopic negative response(PhNR)from photopie electroretinogram(ERG)is a slowly negative potential following positive b wave.The experimental study of primates and clinieal observation of patients determined that PhNR arise from retinal ganglion cells(RGCs)and their axons.But the research result of rodents suggested that PhNR of mice and rats,unlike in human and primates,originate from amaerine cells.Recently,the study progress in PhNR is eoncemed by more and more researchers.The study of PhNR in the focal ERG,the influence of different recording conditions on PhNR wave and the character as well as recording condition of PhNR wave in rodents were introduced in this paper. Key words: Eleetroretinogram; Photopic negative response; Recording condition; Rodent; Focal retina

New Technologies for Glaucoma Imaging

The evolution of imaging technologies over the past decade has reshaped our landscape in diagnosing and managing patients with glaucoma. Adopting technological advances and translating new information into clinical practice pose new challenges to both clinicians and research scientists. This special issue includes five papers covering some of the recent advances in ocular imaging and electrophysiology technologies and demonstrates how such advancement augments our understanding of glaucoma. Since its introduction in 2005, the spectral-domain optical coherence tomography (SD-OCT) has received considerable attention for retinal nerve fiber layer (RNFL) and optic disc imaging. With improved axial resolution to discern individual retinal layers, new parameters such as the ganglion cell complex (GCC) and the photoreceptor layer thicknesses can now be measured reliably with SD-OCT. S. T. Takagi and et al. demonstrate that macular GCC thickness could serve as a biomarker for early detection of glaucoma. With a high density of retinal ganglion cells in the macula, it is conceivable that measuring macular GCC thickness would be valuable for glaucoma assessment. By contrast, the outer retina would be expected to be unaffected. Unexpectedly, N. Fan et al. show that the outer nuclear layer is thicker in mild glaucomatous eyes than in normal eyes. This finding suggests glaucomatous damage may involve structural change in the photoreceptors. Full-field electroretinogram (ERG) has been considered less useful for glaucoma evaluation. S. Machida et al. show that a photopic negative response (PhNR) (a negative deflection following the photopic b-wave) obtained from a focal ERG system could indicate functional abnormality of retinal ganglion cells and has a high diagnostic performance to detect early glaucoma. While the potential of focal ERG PhNR for objective functional assessment appears promising, prospective longitudinal studies are needed to validate its use in glaucoma patients. Intraocular pressure (IOP) is a major risk factor for glaucoma progression. Yet, it has long been recognized that there are factors other than IOP that could modify the course of the disease. In a randomized double-masked study comparing dorzolamide/timolol and latanoprost/timolol fixed combination for treatment in glaucoma patients, I. Januleviciene et al. report that a number of hemodynamic parameters including blood pressure, ocular perfusion pressure, and ophthalmic and central retinal artery vascular resistance are associated with RNFL and/or visual field progression independent of IOP reduction. Although this study is limited by a small sample size (15 patients in each arm) and a high progression rate (40% and 47% of patients progressed, resp.), the result could stimulate more research investigating the roles of ocular and systemic hemodynamics in glaucoma progression. Multiphoton microscopy is a relatively new modality for ophthalmic imaging. E. A. Gibson et al. summarize the applications of multiphoton microscopy for retinal and transscleral imaging and demonstrate the feasibility to visualize the collagen fibers in human trabecular meshwork ex vivo. The exciting development of multiphoton imaging will undoubtedly provide new data for potential application in the clinic in the near future. The improvement in patient care depends upon continued research and development of new tools and new techniques to unfold the pathobiology of glaucoma for early diagnosis and treatment. It is sufficient to say that glaucoma imaging forms one of the cornerstones in the advancement of glaucoma care. Christopher K. S. Leung Felipe A. Medeiros David Garway-Heath David S. Greenfield Robert N. Weinreb

Test of photopic negative response of electroretinogram with DTL electrode in normal Chinese subjects

ObjectiveTo test normal values of photopic negative response (PhNR) of electroretinogram (ERG) with DTL electrode in normal Chinese subjects and to evaluate the characteristic of PhNR.MethodsERGs were recorded on 65 normal subjects (112 eyes) aged 21-76 years using disposable DTL electrodes at full-field ganzfeld brief red flashes on a blue background (luminance of 10 cd/m 2 ).Stimulus flashes of different intensity (1cd·s/m 2 ,5cd·s/m 2 and 7cd·s/m 2 ) were generated by light emitting diodes (LEDs).The amplitudes and latencies of PhNR with age were analyzed.ResultsThe data were divided into 50 years group and ≥50 years group after statistical analysis.The mean latencies in the 50 years group was 65.83±4.06ms,66.17±6.48ms and 65.81±6.71ms at 1,5 and 7 cd·s/m2 respectively which was statistically significant different from that ≥50 years group(69.86±5.68ms,71.33 ± 4.90ms and 70.40±4.61ms,respectively)(P0.001).Mean amplitude of 50 years group was significantly higher than that of ≥50 years group at different stimulus intensities ( -38.94 ± 10.21μV,-38.51± 10.97μV,-38.62± 9.98μV vs-32.41± 7.76μV,-34.52±8.90μV,-33.96± 9.81μV,respectively)(P0.001,P=0.047,P=0.017).ConclusionUse of disposable DTL electrodes can prevent cross infection.Our results record the normal values of PhNR by age group in normal Chinese subjects and provide normal reference limits in clinical practice.

Inter-ocular and inter-session reliability of the electroretinogram photopic negative response (PhNR) in non-human primates

Purpose. To assess the inter-ocular and inter-session reliability for a range of parameters derived from the photopic electroretinogram (ERG) in a group of normal non-human primates. Methods. Inter-ocular differences for photopic ERGs were assessed in a group of normal anesthetized adult rhesus monkeys ( Macaca mulatta, n=29); inter-session reliability was assessed for 23 eyes of 23 animals tested 3 months later. Signals were acquired using Burian-Allen contact lens electrodes, whereby the contralateral cornea served as a reference. Photopic ERGs were elicited using red Ganzfeld flashes (−0·5–0·67 log photopic cd.s m −2) on a rod suppressing blue-background (30 scotopic cd m −2). Measurement reliability was established for a-wave, b-wave, photopic negative response (PhNR) and oscillatory potential (OP) amplitudes, as well as for their implicit times, by calculation of the 95% limits-of-agreement (LOA) and the coefficient-of-variation (COV) for each parameter. Results. OP and a-wave amplitudes increased with intensity up to 0·67 log photopic cd.s m −2, following a typical saturating function, whereas b-wave and PhNR amplitudes both declined above 0·42 log photopic cd.s m −2. Inter-session variability was greater than inter-ocular variability. The inter-session COVs for PhNR amplitude (10–20%) were similar to the other photopic ERG components (a-wave: 12–17%, b-wave: 12–17%, OPs: 13–19%). Inter-session LOAs were also similar across components, but on average, were smallest for responses to moderate intensities (0·0–0·42 log photopic cd.s m −2). Conclusion. In non-human primates, the 95% LOA for inter-session measurements of the photopic ERG a-wave, b-wave, OPs and PhNR are all similar. Inner-retinal damage may best be measured using the PhNR amplitude for moderately bright stimulus intensities. B-wave and PhNR amplitudes for brighter flashes are smaller and more variable. The ratio of PhNR:b-wave amplitudes manifests smaller variability and may therefore be useful for detection of selective PhNR loss.