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Purpose: Our aim was to explore the effect of ambient lighting on the pattern ERG (PERG). Methods: We compared PERGs recorded in two conditions; room lights on and room lights off. PERGs from 21 adult participants were recorded from each eye to high contrast checks of 50' side width, reversing 3rps in a large (30°) and then standard (15°) field. This was performed first in lights-ON conditions, then 2 min after the room lights were switched off. A minimum of 2 averages of 300 trials were acquired for each condition. A subset of 10 participants had PERGs recorded to a 50' check width with a range of stimulus contrasts (96–18%), also to a range of different check widths (100'–12') at high contrast in both ambient lighting conditions in a 30° field. Results: The lights-ON P50 median peak time (PT) was 3 ms earlier than the lights-OFF P50 from the 30° field (range 0–5 ms) and 15° field (range 0–6 ms). The earlier lights-ON P50 PT was evident at different stimulus contrasts, even after accounting for stimulus contrast reductions associated with stray ambient lighting in lights-ON conditions. Lights-OFF and lights-ON P50 PT were similar to different check widths; the lights-OFF P50 PT to a 50' check width matched the lights-ON P50 PT to a 25' check width. Conclusion: PERG P50 PT in lights-ON ambient light conditions can be earlier than in lights-OFF ambient light conditions. The difference in P50 PT with ambient light may reflect alterations in spatial sensitivity associated with retinal adaptation. These results emphasise the clinical importance of consistent ambient lighting for PERG recording and calibration. [ABSTRACT FROM AUTHOR]

This document developed by the International Society for Clinical Electrophysiology of Vision (ISCEV) provides guidance for calibration and verification of stimulus and recording systems specific to clinical electrophysiology of vision. This guideline provides additional information for those using ISCEV Standards and Extended protocols and supersedes earlier Guidelines. The ISCEV guidelines for calibration and verification of stimuli and recording instruments (2023 update) were approved by the ISCEV Board of Directors 01, March 2023. [ABSTRACT FROM AUTHOR]

Objectives:Fixation preference testing is widely used to detect amblyopia, particularly in preverbal children. Pattern electroretinogram (pERG) is an electrophysiological test which is a sensitive indicator of macular function. The aim of this study was to investigate the relationship between fixation preference and macular function on pERG in children with strabismus.Materials and Methods:The study included 11 children with strabismus. All underwent ophthalmological examination including fixation preference by binocular fixation pattern test, best corrected visual acuity (BCVA) assessment, and pERG.Results:The mean age of the patients was 10.09±1.18 years. All patients had unilateral fixation. The mean BCVA was 0.85±0.17 in preferred and 0.48±0.19 in non-preferred eyes (p=0.003). The mean p50 amplitude was 6.07±2.06 μV in preferred and 5.29±2.20 μV in non-preferred eyes (p=0.203), and the mean N95 amplitude was 8.27±2.86 μV and 8.03±3.24 μV respectively (p=0.594). BCVA was correlated with p50 and N95 amplitudes in the non-preferred eyes (p=0.023 and p=0.014). Interocular BCVA difference was correlated with interocular P50 amplitude difference (r=0.688, p=0.019).Conclusion:Although amblyopia is typically considered a cortical phenomenon, future larger studies are needed to investigate the relationship between fixation preference and macular electrophysiological function.

The chick is widely used in studies of eye growth regulation and myopia. The aim of this study was to explore the utility of pattern (p)ERG as a tool to assess retinal function in such studies. Effects of optical defocus and diffusing blur, manipulations used to alter eye growth experimentally, were evaluated. PERGs were recorded from White-Leghorn chickens, using a checkerboard pattern, including 8 spatial frequencies (0.05-2.2c/d SF), 13 contrast levels (1-100%), and 8 temporal reversal frequencies (0.5-20Hz). The acute effects of defocus and diffusing blur were examined. Flash- and pERGs were also recorded from chicks that underwent monocular optic nerve section (ONS), to explore the contribution of retinal ganglion cells (RGCs). Measurements were made up to 6weeks post-ONS, complemented with SD-OCT imaging. In normal chicks, the response to 1Hz, 100% contrast stimuli showed positive- and negative-going waveforms at 43ms (P1) and 75ms (N95), respectively, with 0.06-0.1c/d SF eliciting the largest P1 amplitudes of 21.9±2.5μV. Contrast levels above 5% yielded measurable P1 responses. Responses were transient and monophasic for 0.5-5Hzreversal rates, with higher temporal frequencies yielding steady state responses. Defocus and diffusing blur decreased pERG amplitude across all SFs. pERG responses remained normal after ONS, despite the loss of RGCs. In conclusion, chicks show robust pERG responses, which are attenuated by defocus and diffusing blur. The pERG response is not affected by ONS, suggesting that RGCs do not contribute to the chick pERG.

Objectives: Fixation preference testing is widely used to detect amblyopia, particularly in preverbal children. Pattern electroretinogram (pERG) is an electrophysiological test which is a sensitive indicator of macular function. The aim of this study was to investigate the relationship between fixation preference and macular function on pERG in children with strabismus. Materials and Methods: The study included 11 children with strabismus. All underwent ophthalmological examination including fixation preference by binocular fixation pattern test, best corrected visual acuity (BCVA) assessment, and pERG. Results: The mean age of the patients was 10.09±1.18 years. All patients had unilateral fixation. The mean BCVA was 0.85±0.17 in preferred and 0.48±0.19 in non-preferred eyes (p=0.003). The mean p50 amplitude was 6.07±2.06 µV in preferred and 5.29±2.20 µV in non-preferred eyes (p=0.203), and the mean N95 amplitude was 8.27±2.86 µV and 8.03±3.24 µV respectively (p=0.594). BCVA was correlated with p50 and N95 amplitudes in the non-preferred eyes (p=0.023 and p=0.014). Interocular BCVA difference was correlated with interocular P50 amplitude difference (r=0.688, p=0.019). Conclusion: Although amblyopia is typically considered a cortical phenomenon, future larger studies are needed to investigate the relationship between fixation preference and macular electrophysiological function. [ABSTRACT FROM AUTHOR]

Schizophrenia is a complex disorder that is diagnosed mainly with clinical observation and evaluation. Recent studies suggest that many people with schizophrenia have abnormalities in the function of the N-methyl-d-aspartate receptor (NMDAR). The retina is part of the central nervous system and expresses the NMDAR, raising the possibility of the early detection of NMDAR-related schizophrenia by detecting differences in retinal function. As a first-step, we used two non-invasive outpatient tests of retinal function, the photopic negative response (PhNR) of the light-adapted flash-electroretinogram (PhNR-fERG) and the pattern ERG (PERG), to test individuals with schizophrenia and controls to determine if there were measurable differences between the two populations. The PhNR-fERG showed that males with schizophrenia had a significant increase in the variability of the overall response, which was not seen in the females with schizophrenia. Additionally at the brightest flash strength, there were significant increases in the PhNR amplitude in people with schizophrenia that were maximal in controls. Our results show measurable dysfunction of retinal ganglion cells (RGCs) in schizophrenia using the PhNR-fERG, with a good deal of variability in the retinal responses of people with schizophrenia. The PhNR-fERG holds promise as a method to identify individuals more at risk for developing schizophrenia, and may help understand heterogeneity in etiology and response to treatment. [ABSTRACT FROM AUTHOR]

The aim of our study was to present the different electrophysiological (EF) methods informativity for objective study of the individual retinal layers function in a single patient in order to make a correct diagnosis. Material and Methods: Full field electroretinography (ffERG), multifocal ERG (mfERG), pattern ERG (PERG) and pattern visual evoked potentials (PVEPs) were performed in a single patient. All EF studies were done in a specially equipped, certified electrophysiological laboratory. The research was performed with equipment adjustments according to the latest published ISCEV standards for PERG (2013), PVEPs (2016), ffERG (2015), mfERG(2012). The main variables that were considered in the analysis of EF studies were latency (L) and amplitudes (A), reflecting the configuration of the wave forms. Results: Different EF studies results of a single patient were presented which allow us to make a correct diagnosis. The most pathological were the results of the photopic response in ffERG as well as those from mfERG, which demonstrated generalized retinal damage with predominant cones involvement. PERG and PVEPs which reflect the inner retinal layers function, were very little affected. Conclusion: Knowing all EF methods for vision research and their correct application and results interpretation is of particular importance for the diagnosis and follow-up of a number of congenital and acquired diseases of the visual analyzer. [ABSTRACT FROM AUTHOR]

Purpose: To describe the rapid time course of visual and electroretinographic recovery from vitamin A deficiency in a patient with a history of multiple resected abdominal tumors, including ileal carcinoid and pancreatic adenocarcinoma. Methods: A 61-year-old white man with a history of resected malignant ileal carcinoid and Stage III pancreatic adenocarcinoma referred with complaints of 6 weeks of difficulty with night vision. Results: Initial testing showed significantly reduced scotopic rod responses in both eyes and decreased vitamin A levels and a normal cancer-associated retinopathy laboratory panel. He had complete recovery of both his symptoms and full-field electroretinography within 5 days of starting intramuscular vitamin A. Conclusion: Vitamin A deficiency-related retinopathy after abdominal surgery may be an underreported complication. This case provides a unique clinical perspective in our patient with a history of ileal carcinoid and Stage III pancreatic adenocarcinoma and confirms that rapid symptomatic and electroretinographic recovery is possible with appropriate treatment. [ABSTRACT FROM AUTHOR]

Clinical electrophysiological testing of the visual system incorporates a range of noninvasive tests and provides an objective indication of function relating to different locations and cell types within the visual system. This document developed by the International Society for Clinical Electrophysiology of Vision provides an introduction to standard visual electrodiagnostic procedures in widespread use including the full-field electroretinogram (ERG), the pattern electroretinogram (pattern ERG or PERG), the multifocal electroretinogram (multifocal ERG or mfERG), the electrooculogram (EOG) and the cortical-derived visual evoked potential (VEP). The guideline outlines the basic principles of testing. Common clinical presentations and symptoms are described with illustrative examples and suggested investigation strategies. [ABSTRACT FROM AUTHOR]

The chick is widely used in studies of eye growth regulation and myopia. The aim of this study was to explore the utility of pattern (p)ERG as a tool to assess retinal function in such studies. Effects of optical defocus and diffusing blur, manipulations used to alter eye growth experimentally, were evaluated. PERGs were recorded from White-Leghorn chickens, using a checkerboard pattern, including 8 spatial frequencies (0.05-2.2c/d SF), 13 contrast levels (1-100%), and 8 temporal reversal frequencies (0.5-20Hz). The acute effects of defocus and diffusing blur were examined. Flash- and pERGs were also recorded from chicks that underwent monocular optic nerve section (ONS), to explore the contribution of retinal ganglion cells (RGCs). Measurements were made up to 6weeks post-ONS, complemented with SD-OCT imaging. In normal chicks, the response to 1Hz, 100% contrast stimuli showed positive- and negative-going waveforms at 43ms (P1) and 75ms (N95), respectively, with 0.06-0.1c/d SF eliciting the largest P1 amplitudes of 21.9±2.5μV. Contrast levels above 5% yielded measurable P1 responses. Responses were transient and monophasic for 0.5-5Hzreversal rates, with higher temporal frequencies yielding steady state responses. Defocus and diffusing blur decreased pERG amplitude across all SFs. pERG responses remained normal after ONS, despite the loss of RGCs. In conclusion, chicks show robust pERG responses, which are attenuated by defocus and diffusing blur. The pERG response is not affected by ONS, suggesting that RGCs do not contribute to the chick pERG. [ABSTRACT FROM AUTHOR]

Background: Age-related macular degeneration (AMD) is one of the major causes of progressive and debilitating visual impairment in developed countries and has become a growing health and social issue that needs to be addressed. Imaging techniques and functional tests are useful to assess the degree of macular dysfunction and AMD progression. However, given the slow progression of the disease, it is necessary to identify which techniques are more sensitive for the diagnosis and monitoring of patients with AMD. Purpose: To study changes observed with both imaging techniques and electrophysiological tests in dry AMD-diagnosed patients during 2 years in order to identify the most sensitive technique. Methods: Fundus photography, OCT (macular thickness and number of drusen), Pattern VEP (P100 wave), Pattern ERG (P50 wave) and multifocal ERG (central rings) were carried out in 30 patients that were diagnosed with dry AMD in both eyes. The tests were repeated 1 and 2 years later. Results: No statistically significant changes were observed in visual acuity or in the severity of the disease throughout the study. OCT showed an increase in the number of drusen, as well as in macular thickness. As for the electrophysiological techniques, no significant changes were observed throughout the study in Pattern VEP or Pattern ERG. mfERG showed significant alterations. Statistical analysis showed that mfERG is more efficient in detecting changes throughout the experimental period. Conclusions: OCT and mfERG are useful in the diagnosis and monitoring of dry AMD patients, whilst mfERG is the most sensitive technique to study the progression of this disease in short periods of time. [ABSTRACT FROM AUTHOR]

Background: To evaluate the pattern electroretinogram (PERG) in central serous retinopathy. Methods: In this prospective study, 20 patients with recent onset (<6 weeks) unilateral CSR were studied with the fellow eye acting as control. BCVA, psychophysical parameters, FFA, OCT, flash and pattern ERG were evaluated. Results: The mean P50 amplitude in the affected eye at presentation was 2.36 ± 0.8 μv compared to 3.24 ± 0.85 μv in the normal eye. At 12 weeks, the mean P50 amplitude in the affected eye was 3.16 ± 0.88 μv compared to 3.63 ± 0.82 μv in the normal eye. The reduction of 27 % in P50 amplitude even after recovery was statistically significant ( P < 0.001). A reduction of 19.77 % in the amplitude of N95 wave in the affected eye compared to the normal eye was seen, which was statistically significant ( P < 0.001). In the affected eye, there was statistically significant improvement in the psychophysical tests at 12 weeks. Conclusions: This study reveals that P50 component of the PERG is reduced in cases of CSR, indicating functional disturbance of the macular photoreceptors. A normal flash ERG indicates that pathology is electrophysiologically localised to macula without affecting general retina. Residual deficit in the PERG explains poor quality of vision in spite of normal anatomical apposition and quantitative 6/6 visual acuity. [ABSTRACT FROM AUTHOR]

Aim: To detect early glaucoma, Porciatti and Ventura suggested in 2004 the pattern electroretinogram (PERG) protocol 'PERGLA' with the following features: (1) skin electrodes, (2) steady-state reversal (15 rps) of horizontal 1.6 cpd gratings and (3) Fourier-based analysis. We compared this to our 'PERG Ratio' protocol which uses (1) corneal (DTL) electrodes, (2) nearly the same reversal rate, but 2 check sizes of 0.8° and 16° and (3) Fourier-based analysis using the ratio of amplitudes to the 2 check sizes. Methods: We examined 16 eyes with glaucoma (age 64 ± 7 years) and a control group ( n = 13, age 59 ± 8 years). Responses to all stimuli were simultaneously recorded with both electrode types using PERGLA-type gratings and checkerboards as necessary for the PERG Ratio. Results: The median intra-individual test-retest coefficient of variation in normals pooled across stimuli for skin was 10.0 (95 % CI 1-85 %) and for DTL 9.95 (0.5-49 %), and they are thus nearly identical. The amplitudes obtained from skin were on average 30 % of those with DTL; the skin's signal-to-noise ratio (SNR) was 66 % of DTL electrodes. Glaucoma detection was assessed via receiver operating characteristics (ROCs). Using skin electrodes, ROC area-under-curve (AUC) was 72/76/72 % using gratings (PERGLA), checks or the PERG Ratio, respectively. Using DTL electrodes, the ROC areas were 60/67/77 %; the last value corresponds to the PERG Ratio protocol. Conclusions: Our results suggest that skin electrodes are a valid alternative to corneal electrodes: their advantages being no direct eye contact and smaller normal amplitude range compared to DTL; disadvantages: amplitude reduced to 30 % of DTL and SNR ratio reduced to 66 % of DTL. Efficacy in detecting glaucoma was a little higher with the PERG Ratio protocol (ROC AUC: 77 %, PERGLA: 72 %), but not significantly so. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated contributions from the retinal On and Off pathways, and the spiking and nonspiking activity of neurons in those pathways to the pattern ERG of the mouse. Light-adapted pattern and ganzfeld ERGs were recorded from anesthetized C57BL/6 mice 3–4 months of age. Recordings were made before and after intravitreal injections of PDA (cis-2,3-piperidine-dicarboxylic acid) to block transmission to hyperpolarizing 2nd order and all 3rd order neurons, TTX (tetrodotoxin) to block Na+-dependent spiking, APB (2-amino-4-phosphonobutyric acid) to block synapses between photoreceptors and ON-bipolar cells, and APB + TTX and PDA + TTX cocktails. The pattern stimuli consisted of 0.05 cy/deg gratings reversing in contrast at 1 Hz, presented at various contrasts (50–90%) and a rod saturating mean luminance. For flash ERGs, brief green ganzfeld flashes were presented on a rod-suppressing green background. Recordings were made 39–42 days after unilateral optic nerve crush (ONC) in a subset of animals in which ganglion cell degeneration was subsequently confirmed in retinal sections. Pattern ERGs were similar in waveform for all contrasts, with a positive wave (P1) peak for 90% contrast around 60 ms on average and maximum trough for a negative wave (N2) around 132 ms after each contrast reversal; amplitudes were greatest for 90% contrast which became the standard stimulus. ONC eliminated or nearly eliminated the pattern ERG but did not affect the major waves of the flash ERG. PDA and TTX both delayed P1 and N2 waves of the pattern ERG, and reduced their amplitudes, with effects of PDA on N2 greater than those of TTX. In the flash ERG, PDA reduced a-wave amplitudes, removed OPs but hardly affected b-wave amplitudes. In contrast, TTX reduced b-wave amplitudes substantially, as previously observed in rat. APB removed P1 of the pattern ERG, but left a negative wave of similar timing and amplitude to N2. In the flash ERG, APB removed the b-wave, producing a negative ERG. Addition of TTX to the APB injection removed most of N2 of the pattern ERG, while other waves of the pattern and flash ERG resembled those after APB alone. Addition of TTX to the PDA injection had little effect on the pattern ERG beyond that of PDA alone, but it prolonged the b-wave of the flash ERG. In conclusion, this study confirmed that a selective lesion of ganglion cells will practically eliminate the pattern ERG. The study also showed that P1 of the mouse pattern ERG is dominated by contributions, mainly spiking, from ON pathway neurons, whereas N2 reflects substantial spiking activity from the OFF pathway as well as nonspiking contributions from both pathways. [Copyright &y& Elsevier]

Abstract: The contrast transfer function (CTF) of the pattern electroretinogram (PERG) depends on temporal frequency. For transient stimulation it is fully linear; at faster stimulation rates it becomes strongly non-linear with an accelerated shape. In this study we investigated a range of stimulus parameters with the aim of studying the influence of temporal and spatial frequencies, as well as contrast levels, on the CTF; effects were quantified via an “index of linearity” IL. Both reversal rate and check size influenced linearity (p <.001), examples: At a constant check size of 0.8°, 7.7rps: IL=1.0; 0.8°/24rps: IL=0.5; at a constant reversal rate of 19rps, IL was 0.5 for 0.8°, but rose to 0.8 both for 0.2° and 18°. The reason for this complex response surface remains a puzzle, it cannot be explained by varying parvo/magnocellular contributions, and its possible influences on recordings in patients merit further studies. [Copyright &y& Elsevier]

AimsTo describe the effects of vitamin A deficiency (VAD) on retinal function and the subsequent recovery following treatment in three patients with systemic conditions (two with Crohn disease; one secondary to IgE syndrome).MethodsElectrophysiological testing (including pattern electroretinogram, PERG; electroretinogram, ERG; visual-evoked potential) established the diagnosis of VAD. Repeat testing was carried out in two patients to monitor the time course of recovery following intramuscular vitamin A injection. The third patient had repeat recordings following 13 months of oral supplementation.ResultsAll three patients initially displayed a characteristic absence of rod function associated with VAD. In addition, delayed and reduced amplitude cone ERGs, loss of short wavelength cone (S-cone) function and subnormal macular function were observed in two patients. Restoration of rod and generalised cone function was rapid in the two patients who received intramuscular injection, with normalisation of some electrophysiological responses after only 3 days. Normal S-cone amplitudes and cone latencies were reached within 12 days of vitamin A injection. Macular function returned to within normal limits by 12 days postinjection in one patient, but remained mildly subnormal in the second patient. Full recovery was present after 13 months oral supplementation in the third patient.ConclusionsNovel observations regarding dark-adapted cone function, S-cone function, and PERG are presented. The differences between the effects of VAD on rod and cone function, and their rate of recovery, may reflect differences in the visual cycle between the two photoreceptor classes. The importance of rapidly and accurately diagnosing VAD, a treatable condition, is noted.Eye (2007) 21, 367–376. doi:10.1038/sj.eye.6702212; published online 9 December 2005 [ABSTRACT FROM AUTHOR]

The electrophysiological findings in optic nerve and primary ganglion cell dysfunction are reviewed. The value of the pattern reversal visual-evoked potential (VEP) in the diagnosis of optic nerve disease, and the pattern appearance VEP in the demonstration of the intracranial misrouting associated with albinism, are discussed. The pattern electroretinogram (PERG) is used in the direct assessment of ganglion cell function. The use of PERG or multifocal electroretinography (mfERG), to enable the distinction between VEP delay due to optic nerve disease and that due to macular dysfunction, is described.Eye (2004) 18, 1133-1143. doi:10.1038/sj.eye.6701573 [ABSTRACT FROM AUTHOR]

It has been suggested that low ambient lighting conditions increase the amplitude of the PERG, but no data has been available on this issue. We recorded the transient PERG (0.8° check size) and steady-state PERG (15 rev/s, 0.8° and 16° check size) under three lighting conditions: dark room, only illuminated by the stimulus (resulting in 30 lux), our standard room lighting (windows occluded, one lighted lamp, 200 lux) and fully lit room (full ceiling illumination with eight fluorescent tubes) resulting in rather bright 2300 lux. The stimulus luminance was 50 cd/m2. The sequence of lighting conditions varied for each subject and followed a balanced permutation of an ABCCBA scheme. Results showed a significant effect (P<0.01) across lighting conditions, with no relevant difference between the 30 and 200 lux conditions, but a reduction down to 70% at the 2300 lux condition. This obtained across all check sizes and temporal conditions. As an example, the transient PERG P50-amplitudes were as follows: dark, 5.6±0.8 μV; medium, 5.3±0.6 μV and bright, 3.8± μV (mean ± SEM). Peak times decreased significantly with illumination (dark, medium or bright): 45.9±0.9, 43.1±0.6 or 40.8±0.8 ms. Contrast measurements quantitatively explained the noticeable reduction of PERG amplitude at the brightest illumination level simply by straylight, which reduced the display contrast. This suggests that bright sunlight should be excluded, and that lighting conditions should be moderately standardized at low or medium luminance levels for reproducible amplitudes and peak times. [ABSTRACT FROM AUTHOR]

The aim of the study was to asses the neurosensory retinal function in 12 patients (24 eyes) with different stages of Best's disease, by determining how pattern and full field flash ERG responses were related to visual acuity, stage of disease and extent of visual field loss. All patients had typically abnormal EOG responses and normal full field-flash ERG responses. Patients were stratified in two groups according to visual acuity. In the first group 12 eyes with visual acuity better than 0.5, all amplitudes and latencies of PERG P50 and N95 responses were in the normal range. Small central scotoma was detected by static perimetry in four of these eyes. In the second group of 12 eyes with visual acuity 0.5 or less, PERG showed reduced both P50 and N95 amplitudes in five eyes, and N95 solely, in two eyes. All patients had central scotomas detected by static perimetry. Progression of the disease, seen in deterioration of visual acuity and progression of central visual field defects, corresponded well with reduction of both PERG P50 and N95 amplitudes. There was no correlation found between visual acuity and EOG responses. Our results show that in Best's distrophy, pattern ERG is getting abnormal with progression of the disease, indicating relative preservation of neurosensory retina in initial stages of the disease. In contrast to EOG - being abnormal in all the patients regardless of the stage of disease - and full field-flash ERG - being normal in most of the patients - PERG gives opportunity for electrophysiological determination of the progression of the disease. [ABSTRACT FROM AUTHOR]

Fourier analysis is a powerful tool in signal analysis that can be very fruitfully applied to steady-state evoked potentials (flicker ERG, pattern ERG, VEP, etc.). However, there are some inherent assumptions in the underlying discrete Fourier transform (DFT) that are not necessarily fulfilled in typical electrophysiological recording and analysis conditions. Furthermore, engineering software-packages may be ill-suited and/or may not fully exploit the information of steady-state recordings. Specifically: • In the case of steady-state stimulation we know more about the stimulus than in standard textbook situations (exact frequency, phase stability), so `windowing' and calculation of the `periodogram' are not necessary. • It is mandatory to choose an integer relationship between sampling rate and frame rate when employing a raster-based CRT stimulator. • The analysis interval must comprise an exact integer number (e.g., 10) of stimulus periods. • The choice of the number of stimulus periods per analysis interval needs a wise compromise: A high number increases the frequency resolution, but makes artifact removal difficult; a low number `spills' noise into the response frequency. • There is no need to feel tied to a power-of-two number of data points as required by standard FFT, `resampling' is an easy and efficient alternative. • Proper estimates of noise-corrected Fourier magnitude and statistical significance can be calculated that take into account the non-linear superposition of signal and noise. These aspects are developed in an intuitive approach with examples using both simulations and recordings. Proper use of Fourier analysis of our electrophysiological records will reduce recording time and/or increase the reliability of physiologic or pathologic interpretations. [ABSTRACT FROM AUTHOR]

Previous experiments have shown that the ERG response to alternating gratings vanishes gradually within 4 months after transection of the optic nerve, changes begin after 2-3 weeks. The response to gratings of low spatial frequencies deteriorates earlier than the response to gratings of high spatial frequencies (Maffei and Fiorentini 1981). Quantitative analysis of ganglion cell sizes in retinal wholemounts shows that ganglion cell shrinkage and ganglion cell loss begin at three weeks in the periphery of the retina, particularly in the temporal retina. The same morphological alteration subsequently becomes apparent also in the area centralis and the nasal retina, respectively. The main and early cell loss occurs among medium sized ganglion cells, supposedly the beta-cells. Among the alpha-cells only shrinkage is observed up to two months postoperatively. Light- and electron microscopic examination of cross sections through the retina show that pathological changes are restricted to the innermost layers. [ABSTRACT FROM AUTHOR]

Objectives: Fixation preference testing is widely used to detect amblyopia, particularly in preverbal children. Pattern electroretinogram (pERG) is an electrophysiological test which is a sensitive indicator of macular function. The aim of this study was to investigate the relationship between fixation preference and macular function on pERG in children with strabismus., Materials and Methods: The study included 11 children with strabismus. All underwent ophthalmological examination including fixation preference by binocular fixation pattern test, best corrected visual acuity (BCVA) assessment, and pERG., Results: The mean age of the patients was 10.09±1.18 years. All patients had unilateral fixation. The mean BCVA was 0.85±0.17 in preferred and 0.48±0.19 in non-preferred eyes (p=0.003). The mean p50 amplitude was 6.07±2.06 μV in preferred and 5.29±2.20 μV in non-preferred eyes (p=0.203), and the mean N95 amplitude was 8.27±2.86 μV and 8.03±3.24 μV respectively (p=0.594). BCVA was correlated with p50 and N95 amplitudes in the non-preferred eyes (p=0.023 and p=0.014). Interocular BCVA difference was correlated with interocular P50 amplitude difference (r=0.688, p=0.019)., Conclusion: Although amblyopia is typically considered a cortical phenomenon, future larger studies are needed to investigate the relationship between fixation preference and macular electrophysiological function.

This chapter reviews common applications of visual electrophysiology relevant to neuro-ophthalmology practice. The use of standard tests and extended protocols are described including the cortical visual evoked potential and pattern and full-field electroretinogram (PERG; ERG) methods, the latter including the photopic negative response. Abnormalities of these recordings are rarely specific but provide valuable diagnostic guidance and an objective measure of visual pathway function, difficult or impossible to infer by other methods. The electrophysiological phenotypes associated with Leber hereditary optic neuropathy, OPA1- and SSBP1-associated dominant optic atrophy, and WFS1-related syndromes are described. Typical changes in retinal and optic nerve function tests associated with acquired disease are highlighted, including those related to demyelination, ischemic, compressive, nutritional and toxic, and nonorganic etiologies. The importance of complementary testing using different electrophysiological techniques is emphasized, for the purposes of differential diagnosis and in disorders that may masquerade as optic nerve pathology., (Copyright © 2021 Elsevier B.V. All rights reserved.)