Implicit Times Research Articles

Electrophysiological function in eyes with reticular pseudodrusen according to fundus distribution.

Reticular pseudodrusen (RPD) could be present not only in the posterior pole but extramacular area also as a confluent morphological pattern. Thus RPD can be classified by the fundus distribution for the assessment of visual prognosis. The electrophysiological function in eyes with reticular pseudodrusen (RPD), showing various fundus distribution were evaluated using full-field electroretinogram (ERG). Retinal distribution of RPD was divided into three types (localized, intermediate, and diffuse) according to the extent of involvement of retinal areas by fundus photograph montages. RPD were present with the diffuse type in 21 eyes (25.6%), with the intermediate type in 30 eyes (36.6%), and with the localized type in 31 eyes (37.8%). The average age was 74.76 ± 4.52 (range, 65–81) years in the diffuse type, 72.47 ± 9.13 (range, 55–91) years in the intermediate type, and 70.26 ± 7.77 (range, 61–89) years in the localized type. The mean amplitudes of the scotopic rod response, scotopic maximal combined response, oscillatory potentials (OP), photopic cone response, and 30Hz cone flicker response were more decreased in the diffuse, intermediate, and localized types in order, except for the photopic cone a-wave response. The diffuse type showed reduced amplitudes of ERG responses than the normal control group under all testing conditions except for the photopic a-wave response, and differences were statistically significant with the age restriction and adjustment methods (Bonferroni-corrected P < 0.05). The mean implicit times of ERG responses were significantly delayed in the diffuse type in the photopic b-wave. (Bonferroni-corrected P < 0.05). Extensive retinal involvement of RPD correlates with severely reduced electrophysiological retinal function. This acquired form of decreased electrophysiological function should be regarded as different from those of hereditary retinal degeneration.

Early and localized retinal dysfunction in patients with type 1 diabetes mellitus studied by multifocal electroretinogram.

To investigate the function of localized retinal areas in highly selected type 1 diabetes mellitus patients (DM1) with no or mild signs of diabetic retinopathy (NO DR and NPDR, respectively) and its correlation with age, diabetes duration and glycemic control. Multifocal electroretinograms (mfERG) were recorded in 35 eyes of 18 NO DR patients and 38 eyes of 19 NPDR patients. Thirty-one eyes of 17 normal subjects were enrolled as controls. N1-P1 response amplitude densities (RADs) and P1 implicit times (ITs) from isolated (R1: 0°-2.5°, R2: 2.5°-5°, R3: 5°-10°) and combined (R1 + R2, R2 + R3 and R1 + R2 + R3) annular rings and from four retinal sectors (nasal, N; temporal, T; superior, S and inferior, I) with increasing eccentricities up to 10° (S1, S2, S3, S1 + S2, S1 + S2 + S3) were measured. The statistical differences between DM1 groups and controls were tested by ANOVA. The electrophysiological data were correlated with age, duration of diabetes and glycated hemoglobin (HbA1c) level using the Pearson's test. MfERG RADs, but not ITs, from all isolated and combined rings and sectors up to 10° of foveal eccentricity were statistically different between DM1 groups compared to controls. No significant differences were found between NO DR and NPDR patients. The mfERG abnormalities of the central retinal areas were correlated significantly with age in both DM1 groups and with diabetes duration mainly in NPDR group. In DM1 patients, localized retinal dysfunction, described by reduced mfERG RAD, can be observed also in the absence of clinical signs of DR and it is related to aging.

Long-Term Functional and Structural Consequences of Primary Blast Overpressure to the Eye.

Acoustic blast overpressure (ABO) injury in military personnel and civilians is often accompanied by delayed visual deficits. However, most animal model studies dealing with blast-induced visual defects have focused on short-term (≤1 month) changes. Here, we evaluated long-term (≤8 months) retinal structure and function deficits in rats with ABO injury. Adult male Long-Evans rats were subjected to ABO from a single blast (approximately 190 dB SPL, ∼63 kPa, @80 psi), generated by a shock tube device. Retinal function (electroretinography; ERG), visual function (optomotor response), retinal thickness (spectral domain-optical coherence tomography; SD-OCT), and spatial cognition/exploratory motor behavior (Y-maze) were measured at 2, 4, 6, and 8 months post-blast. Immunohistochemical analysis of glial fibrillary acidic protein (GFAP) in retinal sections was performed at 8 months post-blast. Electroretinogram a- and b-waves, oscillatory potentials, and flicker responses showed greater amplitudes with delayed implicit times in both eyes of blast-exposed animals, relative to controls. Contrast sensitivity (CS) was reduced in both eyes of blast-exposed animals, whereas spatial frequency (SF) was decreased only in ipsilateral eyes, relative to controls. Total retinal thickness was greater in both eyes of blast-exposed animals, relative to controls, due to increased thickness of several retinal layers. Age, but not blast exposure, altered Y-maze outcomes. GFAP was greatly increased in blast-exposed retinas. ABO exposure resulted in visual and retinal changes that persisted up to 8 months post-blast, mimicking some of the visual deficits observed in human blast-exposed patients, thereby making this a useful model to study mechanisms of injury and potential treatments.

Macular dysfunction in patients with macula-on rhegmatogenous retinal detachments

AimsTo assess macular function in patients with macula-on rhegmatogenous retinal detachments (RRDs) using focal macular electroretinography (FMERG).MethodsThis is a prospective, observational case series of 27 patients diagnosed with a macula-on...

Impact of Choriocapillaris Flow on Multifocal Electroretinography in Intermediate Age-Related Macular Degeneration Eyes.

To investigate the relationship between perfusion of the choriocapillaris (CC) and macular function in eyes with intermediate age-related macular degeneration. In this prospective, observational, cross-sectional study, macular optical coherence tomography angiography images and multifocal electroretinograms were obtained in 20 eyes with intermediate age-related macular degeneration from 20 patients. The main outcome measures were (1) the percent nonperfused choriocapillaris area (PNPCA), which represents a measure of the total area of CC vascular dropout, and (2) the average size of the CC signal voids, which represent contiguous regions of CC dropout. Furthermore, amplitude and implicit time of multifocal electroretinograms N1 and P1 waves in the two central rings (R1 and R2) were included in the analysis. Of the 20 patients enrolled, only 17 eyes from 17 patients (13 women) were included in this analysis. Three patients were excluded because of poor scan quality. Mean ± SD age was 75.1 ± 7.9 years (range, 62-89 years). The best corrected visual acuity was 0.17 ± 0.13 logarithm of the minimum angle of resolution. In univariate analysis, both the PNPCA and average signal void size were found to have a significant direct relationship with N1 implicit time in the R2 ring (P = 0.006 and P = 0.035, respectively). Neither PNPCA nor the average signal void size was associated with P1 or N1 implicit times in R1. In intermediate age-related macular degeneration eyes, PNPCA and average signal void size are related to N1 multifocal electroretinogram implicit times, which suggests an association between CC perfusion and photoreceptor function.

Longitudinal Study of Visual Function in Vogt-Koyanagi-Harada Disease Using Full-Field Electroretinography

To investigate the dynamic changes of full-field electroretinography (ffERG) and its relationship with structural changes in Vogt-Koyanagi-Harada (VKH) disease. Interventional case series. A total of 42 VKH patients (84 eyes) and 45 normal controls (90 eyes) were included in this study. All of the patients showed active uveitis and were referred to us within 2months after disease onset. Dynamic changes of retinal function were evaluated by ffERG before treatment and 2, 6, and 12months after treatment with systemic corticosteroids and cyclosporine. The relationship between ffERG data with structural changes as disclosed by B-scan ultrasonography, fundus fluorescein angiography (FFA), indocyanine green angiography, and optical coherence tomography were also evaluated. All investigated VKH patients showed a significantly decreased visual acuity and retinal structural changes before treatment. These changes significantly improved at 2months and no abnormalities were apparent at 6months following treatment. Full-field ERG showed significantly decreased amplitudes and prolonged implicit times for all dark-adapted (DA) and light-adapted ffERG responses before treatment. All these parameters, except the a-wave amplitude in the DA response, were improved at 2months and returned to the normal level at 12months. Our findings show that ffERG is a more sensitive method to detect improvement of visual function in VKH following treatment when compared to corrected distance visual acuity and the various imaging techniques to detect structural abnormalities in VKH.

TrkB signalling pathway mediates the protective effects of exercise in the diabetic rat retina.

Diabetic retinopathy is a leading cause of vision loss. Treatment options for early retinopathy are sparse. Exercise protects dying photoreceptors in models of retinal degeneration, thereby preserving vision. We tested the protective effects of exercise on retinal and cognitive deficits in a type 1 diabetes model and determined whether the TrkB pathway mediates this effect. Hyperglycaemia was induced in Long Evans rats via streptozotocin injection (STZ; 100mg/kg). Following confirmed hyperglycaemia, both control and diabetic rats underwent treadmill exercise for 30min, 5days/week at 0m/min (inactive groups) or 15m/min (active groups) for 8weeks. A TrkB receptor antagonist (ANA-12), or vehicle, was injected 2.5h before exercise training. We measured spatial frequency and contrast sensitivity using optokinetic tracking biweekly post-STZ; retinal function using electroretinography at 4 and 8weeks; and cognitive function and exploratory behaviour using Y-maze at 8weeks. Retinal neurotrophin-4 was measured using ELISA. Compared with non-diabetic controls, diabetic rats showed significantly reduced spatial frequency and contrast sensitivity, delayed electroretinogram oscillatory potential and flicker implicit times and reduced cognitive function and exploratory behaviour. Exercise interventions significantly delayed the appearance of all deficits, except for exploratory behaviour. Treatment with ANA-12 significantly reduced this protection, suggesting a TrkB-mediated mechanism. Despite this, no changes in retinal neurotrohin-4 were observed with diabetes or exercise. Exercise protected against early visual and cognitive dysfunction in diabetic rats, suggesting that exercise interventions started after hyperglycaemia diagnosis may be a beneficial treatment. The translational potential is high, given that exercise treatment is non-invasive, patient controlled and inexpensive.

Flicker electroretinograms of eyes with cataract recorded with RETeval system before and after mydriasis.

PurposeThe aim of this study is to determine the effect of pupil size of eyes with cataracts on the flicker electroretinograms (ERGs) elicited and recorded with the RETeval system.Patients and methodsForty-one eyes of 41 patients (mean age, 76.5±7.3 years) that had grade 2 nuclear or cortical cataract without any other abnormalities were studied. Flicker ERGs were recorded before and after mydriatic drops instillation. The ERGs were elicited by the white light delivered at the frequency of 28.3 Hz and intensities of 2, 8, and 32 Td-s. The amplitudes and the implicit times of the flicker ERGs before and after mydriasis were compared.ResultsThere were no significant differences between the amplitudes before and after mydriasis (P=0.35, 2 Td-s; P=0.31, 8 Td-s; P=0.50, 32 Td-s). There were also no significant differences between the implicit times before and after mydriasis (P=0.86, 2 Td-s; P=0.98, 8 Td-s; P=0.95, 32 Td-s). The mean amplitudes and implicit times of the nuclear and cortical cataracts groups before the mydriasis were also not significantly different from those after mydriasis for all stimulus intensities.ConclusionThe lack of significant differences in the amplitudes and the implicit times of the flicker ERG of cataractous eyes before and after mydriasis indicated that the RETeval flicker ERGs in cataractous eyes is less affected by the pupil diameter. With our earlier study, it was assumed that the effect of cataracts on the RETeval flicker ERGs was due to the opacity of the crystalline lens, and the influence of the cataract would not be reduced or increased by mydriasis.

Three Dimensional Stimulus Source for Pattern Electroretinography in Mid- and Far-peripheral Retina.

PurposeThe pattern electroretinogram (pERG) response reflects, in part, ganglion cell function. However, probing retinal ganglion cell (RGC) function in the mid- and far peripheral retina is difficult with conventional flat-panel pERG stimulus sources. A pattern stimulus source is presented for probing the peripheral retina. Peripheral pERG (ppERG) responses were evaluated versus luminance, reversal rate, and field subtended, and were compared with conventional pERG in healthy eyes.MethodsEleven normally-sighted subjects were recruited. A hemispherical surface was used to present a reversing checkerboard pattern to the peripheral retina, from approximately 35° to 85° of visual field, in all directions. Responses to stimuli presented to peripheral field sectors (superior, nasal, inferior, temporal) were also recorded. Conventional pERG responses were recorded on the same day. Amplitudes and implicit times of waveform peaks were evaluated.ResultsRobust pERG responses from peripheral retina resemble conventional pERG responses but with shorter implicit times and reduced positive component. Responses to high-luminance patterns include high-frequency components resembling flash ERG oscillatory potentials. Negative response component amplitudes increased with increasing pattern luminance, and decreased with increasing reversal rate.ConclusionsPeripheral-field pERG responses are robust and repeatable; the unique response properties reflect differences between central and peripheral retina. Field-sector response ratios can be used to probe for sectoral dysfunction associated with disease.Translational RelevanceThe ppERG approach provides direct measurement of proximal retinal function beyond the fields probed by conventional perimetry and pERG, providing access to a relatively under studied part of the retina relevant to early stage glaucoma.

Effects of dexamethasone implant on multifocal electroretinography in central retinal vein occlusion

Purpose:To investigate the effect of Ozurdex (dexamethasone intravitreal implant) on multifocal electroretinography (mfERG) findings during the treatment of macular edema secondary to the central retinal vein occlusion (CRVO).Methods:Fifteen eyes of 15 patients who were treated with Ozurdex implant due to CRVO-related macular edema were included in this study. Best corrected visual acuity (BCVA), central macular thickness (CMT), and mfERG evaluations were performed for all patients before injection of Ozurdex. After the injection, BCVA and CMT were measured at months 3 and 6 and mfERG test was performed at month 6 for all patients.Results:Pre-implantation mfERG P wave amplitude values of r1, r2, r3, r4 and r5 were 57.8 ± 14.8, 25.1 ± 10.6, 17.2 ± 7.3, 12.0 ± 5.0 and 7.1 ± 3.6 nV/deg2, respectively. They increased to 72.9 ± 33.2, 31.2 ± 9.3, 22.6 ± 7.6, 15.6 ± 7.1 and 10.9 ± 5.7 nV/deg2, respectively, at month 6. However, these increases were not statistically significant (all P > 0.05). Pre-implantation mfERG r1, r2, r3, r4 and r5 P wave implicit times were 40.1 ± 10.9, 39.4 ± 3, 38.4 ± 3.4, 38.2 ± 3.1 and 39.3 ± 2.2 ms, respectively and these values were measured as 38.9 ± 8.2, 38.4 ± 4.7, 37 ± 3.8, 37.5 ± 4.6 and 37.7 ± 4.7 ms at 6 months. Although there were reductions in P wave implicit times in all rings, they were not statistically significant (all P > 0.05).Conclusion:In this prospective study, we found that the Ozurdex implant had no effect on mfERG findings 6 months after insertion for treatment of CRVO-related macular edema.

The Contribution of L-Type Cav1.3 Channels to Retinal Light Responses.

L-type voltage-gated calcium channels (LTCCs) regulate tonic neurotransmitter release from sensory neurons including retinal photoreceptors. There are three types of LTCCs (Cav1.2, Cav1.3, and Cav1.4) expressed in the retina. While Cav1.2 is expressed in all retinal cells including the Müller glia and neurons, Cav1.3 and Cav1.4 are expressed in the retinal neurons with Cav1.4 exclusively expressed in the photoreceptor synaptic terminals. Mutations in the gene encoding Cav1.4 cause incomplete X-linked congenital stationary night blindness in humans. Even though Cav1.3 is present in the photoreceptor inner segments and the synaptic terminals in various vertebrate species, its role in vision is unclear, since genetic alterations in Cav1.3 are not associated with severe vision impairment in humans or in Cav1.3-null (Cav1.3−/−) mice. However, a failure to regulate Cav1.3 was found in a mouse model of Usher syndrome, the most common cause of combined deafness and blindness in humans, indicating that Cav1.3 may contribute to retinal function. In this report, we combined physiological and morphological data to demonstrate the role of Cav1.3 in retinal physiology and function that has been undervalued thus far. Through ex vivo and in vivo electroretinogram (ERG) recordings and immunohistochemical staining, we found that Cav1.3 plays a role in retinal light responses and synaptic plasticity. Pharmacological inhibition of Cav1.3 decreased ex vivo ERG a- and b-wave amplitudes. In Cav1.3−/− mice, their dark-adapted ERG a-, b-wave, and oscillatory potential amplitudes were significantly dampened, and implicit times were delayed compared to the wild type (WT). Furthermore, the density of ribbon synapses was reduced in the outer plexiform layer of Cav1.3−/− mice retinas. Hence, Cav1.3 plays a more prominent role in retinal physiology and function than previously reported.

Assessment of macular function in patients with idiopathic Epiretinal membrane by multifocal Electroretinography: correlation with visual acuity and optical coherence tomography

BackgroundThis study evaluates the macular function changes in patients with idiopathic macular epiretinal membrane (ERM) by multifocal electroretinography (mfERG) and their correlations with visual acuity and central macular thickness (CMT) by optical coherence tomography (OCT).MethodsTwenty eyes of 20 patients with ERM underwent OCT and mfERG examinations. The response amplitude densities and implicit times of mfERG were compared to the control fellow eyes. Correlation analyses among visual acuity, central macular thickness and mfERG values in the central two concentric rings were performed.ResultsThe mfERG P1 response amplitude densities in ring 1–2 and P1 implicit time in ring1 were significantly changed in epiretinal membrane eyes compared with controls (P < 0.05). Multivariate stepwise linear regression analyses showed LogMAR visual acuity was significantly correlated with CMT (P = 0.004), and also with the P1 amplitude density in ring 1 (P = 0.002). CMT showed significant correlation with P1 implicit time in ring 2 (P = 0.013).ConclusionsThe mfERG abnormalities show macular function changes and correlate with visual acuity and central macular thickness in eyes with ERM. In first-order mfERG responses, P1 wave changes may be a sensitive functional measurement for ERM patients.

A Temporal White Noise Analysis for Extracting the Impulse Response Function of the Human Electroretinogram.

PurposeWe introduce a method for determining the impulse response function (IRF) of the ERG derived from responses to temporal white noise (TWN) stimuli.MethodsThis white noise ERG (wnERG) was recorded in participants with normal trichromatic vision to full-field (Ganzfeld) and 39.3° diameter focal stimuli at mesopic and photopic mean luminances and at different TWN contrasts. The IRF was obtained by cross-correlating the TWN stimulus with the wnERG.ResultsWe show that wnERG recordings are highly repeatable, with good signal-to-noise ratio, and do not lead to blink artifacts. The wnERG resembles a flash ERG waveform with an initial negativity (N1) followed by a positivity (P1), with amplitudes that are linearly related to stimulus contrast. These N1 and N1-P1 components showed commonalties in implicit times with the a- and b-waves of flash ERGs. There was a clear transition from rod- to cone-driven wnERGs at ∼1 photopic cd.m−2. We infer that oscillatory potentials found with the flash ERG, but not the wnERG, may reflect retinal nonlinearities due to the compression of energy into a short time period during a stimulus flash.ConclusionThe wnERG provides a new approach to study the physiology of the retina using a stimulation method with adaptation and contrast conditions similar to natural scenes to allow for independent variation of stimulus strength and mean luminance, which is not possible with the conventional flash ERG.Translational RelevanceThe white noise ERG methodology will be of benefit for clinical studies and animal models in the evaluation of hypotheses related to cellular redundancy to understand the effects of disease on specific visual pathways.

Effect of axial length on full‐field and multifocal electroretinograms

PurposeThe aim was to investigate the effect of axial length on full‐field electroretinogram (ffERG) and multifocal electroretinogram (mfERG) in young Indian subjects.MethodsOne hundred subjects (44 male) with refractive errors from +0.50 to −18.00 DS and no myopic retinopathy underwent axial length measurement. ffERG was measured, which included scotopic and photopic responses according to International Society for Clinical Electrophysiology of Vision (ISCEV) guidelines. The mfERG was recorded after correcting for refractive error according to ISCEV standards. The dark‐adapted and light‐adapted parameters of ffERG and N1, P1 parameters of six rings in mfERG were analysed with axial length, controlled for refractive error. The subjects were divided into seven groups based on axial length. The b/a ratio of dark‐adapted and light‐adapted 3.0 ffERG and P1/N1 ratio of mfERG amplitudes were analysed for seven groups of axial length.ResultsThe axial length ranged from 21.79 to 30.55-mm. Significant negative correlations were noted for ffERG and mfERG amplitudes, whereas implicit times showed minimal delay with increase in axial length. In ffERG, the scotopic responses were more decreased compared to photopic responses. In mfERG, P1 and N1 amplitudes were significantly decreased in all the rings in all groups and more reduction was noted in the central ring compared to peripheral rings. The P1 amplitudes were more affected as compared to N1 amplitudes. The light‐adapted and dark‐adapted 3.0 ERG b/a ratio and P1/N1 ratio for seven axial length groups did not show statistically significant difference. The ERG parameters were not significant with refractive error.ConclusionThis study quantifies the relationship of axial length with ffERG and mfERG parameters in a young Indian population. Although the amplitudes were reduced significantly, the implicit times were not significantly affected. The ERG parameters were more related to axial length than refractive error. Hence, interpretation of ffERG and mfERG parameters needs careful consideration in subjects with increasing axial length.

Relationship between functional and structural retinal changes in myopic eyes

BackgroundThe aim of this study was to investigate the retinal structure in different grades of myopia and correlate it with the functional changes detected with multifocal electroretinogram (mf‐ERG) and try to show the most important determining factors.MethodsThe study included 80 participants divided into four groups according to their spherical equivalent refractive error, namely, emmetropia (within ± 0.50 D), mild myopia group (greater than −0.50 to −3.00 D), moderate myopia group (more than −3.00 to −6.00 D) and high myopia group (greater than −6.00 D). Full ophthalmologic examination was performed for all participants, including visual acuity (VA), slitlamp examination, Goldmann applanation tonometry, indirect ophthalmoscopy, axial length (AL) measurement, retinal nerve fibre layer thickness assessment and mf‐ERG stimulation.ResultsAxial length was significantly higher in myopes than emmetropes; also it was higher the greater the degree of myopia. There was a reduction in the amplitude and prolongation of implicit times of mf‐ERG in myopia. Also P1 implicit time of the mf‐ERG response was prolonged the greater the degree of myopia. The retinal nerve fibre layer was significantly thinner in myopic groups than the emmetropic group. The thinning of the retinal nerve fibre layer increased the more the degree of myopia. Multiple regression analysis of myopic patients showed that AL is the most important determinant of most of the mf‐ERG five‐rings retinal response density (RRD), mf‐ERG four‐quadrant (Q) RRD, most of the five‐rings P1 amplitude and all five‐rings latencies. The most important determinant factors of mean Q RRD were VA, AL and retinal nerve fibre layer thickness.ConclusionThe retina of the myope is subject to both structural and functional alterations compared to that of the emmetrope. Significant correlations exist between the functional and structural changes and can be explained on bases of longer AL and increasing myopic refraction.

Subclinical Decrease in Central Inner Retinal Activity Is Associated With Myopia Development in Children.

To investigate the characteristics of retinal electrophysiological activity in relation to early myopia development in children. Fifty-six children aged 6 to 9 years with emmetropic refractive error (defined as ≥ -0.5 diopter [D] and ≤ +0.5 D) were recruited. Cycloplegic refraction, axial length, and global flash multifocal electroretinogram (MOFO mfERG) at 49% and 96% contrast levels were recorded in all children at their first visit. The refraction and axial length measurements were repeated after 1 year. The amplitudes and implicit times of the direct component (DC) and the induced component (IC) of the MOFO mfERG obtained at the initial visit were analyzed. Correlations between the MOFO mfERG parameters and changes in refractive error and axial length were investigated. The mean spherical equivalent refractive error and axial length of the eyes of the children at the first visit were +0.19 ± 0.33 D and 23.14 ± 0.6 mm, respectively. After 1 year, the mean refractive error increased by -0.55 ± 0.53 D, whereas axial length increased by 0.37 ± 0.22 mm. The changes in refractive error and axial length were significantly correlated with the central IC amplitudes at 49% contrast level measured at the initial visit (ρ = 0.46, P < 0.001 and ρ = -0.34, P = 0.01, respectively). The prospective changes we have shown are believed to derive from central inner retina. These changes appear to precede myopia and could be a potential reference for juvenile myopia development.

Factors Affecting Mydriasis-Free Flicker ERGs Recorded With Real-Time Correction for Retinal Illuminance: Study of 150 Young Healthy Subjects.

A small, full-field flicker electroretinogram (ERG) recording system was recently developed to record flicker ERGs without mydriasis (RETeval). The device delivers a stimulus with constant retinal illuminance by adjusting the retinal luminance to compensate for changes in the pupillary area. The purpose of this study was to determine what factors affect the fundamental components of the flicker ERGs recorded by RETeval in young healthy subjects. Flicker ERGs were recorded with the RETeval system from 150 eyes of 150 young healthy subjects (age, 20-29 years). Univariate and multivariate linear regression analyses were performed to identify the factors that affected the implicit times and amplitudes of the fundamental component of the flicker ERGs. The independent variables included age, sex, refractive error, axial length, and pupillary area. Multivariate regression analyses indicated that a longer axial length (P = 0.03) and larger pupillary area (P = 0.008) were independent factors that were significantly associated with longer implicit times of the fundamental component of the flicker ERGs. Multivariate regression analyses also showed that the female sex (P = 0.03) was an independent factor, which was significantly associated with larger amplitude fundamental component of the flicker ERGs. These results indicate that the fundamental components of the RETeval flicker ERGs are significantly affected by the axial length, pupillary area, and sex of young healthy subjects. The results also suggest that it would be better to compensate for the Stiles-Crawford effect when flicker ERGs are recorded with natural pupils.

Electrophysiological Studies on The Dynamics of Luminance Adaptation in the Mouse Retina.

To date, most studies involving in vivo electroretinography in mice are performed on steady state adapted animals. In this study, we focused on the dynamics of adaptation to high and low light levels in the mouse retina. Two flash electroretinogram (ERG) protocols and one flicker ERG protocol were employed. In the two flash ERG protocols, the animals were adapted to either 25 or 40 cd/m2 white light and ERGs were recorded for up to 15 min of adaptation. Afterwards, flash ERGs were recorded for up to 45 min of dark adaptation. Amplitudes of the flash ERG increased during light adaptation, while implicit times of the different wave components decreased. During subsequent dark adaptation, the amplitudes further increased. The increase in a-to-b-wave ratio indicated adaptational processes at the photoreceptor synapse. In the flicker ERG protocol, the responses to 12 Hz sinusoidal luminance modulation during the adaptation to 25 cd/m2 and a 1 cd/m2 mean luminances were recorded. The amplitudes of the first harmonic components in the flicker protocol decreased during light adaptation but increased during dark adaptation. This is at odds with the changes in the flash ERG, indicating that adaptation may be different in different retinal pathways.

Multifocal Electroretinography in Patients with Poppers Maculopathy

Maculopathy is a potential side effect of amyl nitrite or "poppers" abuse. It is characterized by a sudden, painless decrease in visual acuity. While the funduscopic changes are subtle, optical coherence tomography shows alterations of the outer retinal layers in the fovea. However, the extent of retinal dysfunction remains poorly understood. We compared the multifocal electroretinogram of 6 patients with poppers maculopathy to that of a control group consisting of 6 healthy subjects. Response densities and implicit times of N1 and P1 were analyzed. Response densities and implicit times of both N1 and P1 were lower in the patients with poppers maculopathy than in the control group, particularly in ring 1 and rings 4 and 5. The only statistically significant finding, however, was a reduced N1 response density of one hexagon in the patient group. No significant differences were found considering the sum response or the averaged rings 1 to 5. Compared to a healthy control group, the multifocal electroretinogram of patients with poppers maculopathy shows no relevant impairment. This contrasts the marked effect of the disease on visual acuity. In clinical practice, poppers maculopathy cannot be diagnosed by multifocal electroretinography.

Nonsedated handheld electroretinogram as a screening test of retinal dysfunction in pediatric patients with nystagmus

To assess the feasibility, sensitivity, and specificity of nonsedated handheld cone flicker electroretinogram (ERG) as a screening tool to detect retinal dysfunction in children with nystagmus. Pediatric patients at a tertiary referral center from December 2015 to July 2016 were enrolled and placed into three age-matched groups: normal, nystagmus with a retinal dystrophy, and nystagmus without a retinal dystrophy. Unsedated 30Hz cone flicker ERG responses were obtained using a handheld device (RETeval) from both eyes of each patient using skin electrode sensors after pupillary dilation. A total of 71 children were enrolled; amplitudes and implicit times were successfully obtained in 65 (92%): 31 (mean age±SD, 5.6±2.7years; range, 1-12years) without nystagmus and 34 with nystagmus. Nystagmus patients were grouped by those with (n=15; mean age, 8.5±4.5 [range, 2-17years) and without (n=19; mean age, 4.3±3.0 [range, 6 months-10 years]) a retinal dystrophy. The patients with retinal dystrophies had significantly smaller amplitudes and prolonged or nonmeasurable implicit times than the other two groups (P<0.001). Among nystagmus patients, amplitude was able to discriminate between those with and without retinal dystrophies with area under curve of 0.986 (SE=0.016; P<0.001). An amplitude <5μV in combination with an implicit time of >33ms warrants further evaluation. Unsedated handheld cone flicker ERG is a feasible screening test that effectively detects retinal dysfunction in children with nystagmus. In conjunction with clinical findings, the test helps reduce the need for sedated ERG in children.