Visual Evoked Response Imaging System Research Articles

Test-retest reliability of the multifocal photopic negative response.

To assess the test-retest reliability of the multifocal photopic negative response (mfPhNR) of normal human subjects. Multifocal electroretinograms were recorded from one eye of 61 healthy adult subjects on two separate days using a Visual Evoked Response Imaging System software version 4.3 (EDI, San Mateo, California). The visual stimulus delivered on a 75-Hz monitor consisted of seven equal-sized hexagons each subtending 12° of visual angle. The m-step exponent was 9, and the m-sequence was slowed to include at least 30 blank frames after each flash. Only the first slice of the first-order kernel was analyzed. The mfPhNR amplitude was measured at a fixed time in the trough from baseline (BT) as well as at the same fixed time in the trough from the preceding b-wave peak (PT). Additionally, we also analyzed BT normalized either to PT (BT/PT) or to the b-wave amplitude (BT/b-wave). The relative reliability of test-retest differences for each test location was estimated by the Wilcoxon matched-pair signed-rank test and intraclass correlation coefficients (ICC). Absolute test-retest reliability was estimated by Bland-Altman analysis. The test-retest amplitude differences for neither of the two measurement techniques were statistically significant as determined by Wilcoxon matched-pair signed-rank test. PT measurements showed greater ICC values than BT amplitude measurements for all test locations. For each measurement technique, the ICC value of the macular response was greater than that of the surrounding locations. The mean test-retest difference was close to zero for both techniques at each of the test locations, and while the coefficient of reliability (COR-1.96 times the standard deviation of the test-retest difference) was comparable for the two techniques at each test location when expressed in nanovolts, the %COR (COR normalized to the mean test and retest amplitudes) was superior for PT than BT measurements. The ICC and COR were comparable for the BT/PT and BT/b-wave ratios and were better than the ICC and COR for BT but worse than PT. mfPhNR amplitude measured at a fixed time in the trough from the preceding b-wave peak (PT) shows greater test-retest reliability when compared to amplitude measurement from baseline (BT) or BT amplitude normalized to either the PT or b-wave amplitudes.

Multifocal electroretinography in type 2 idiopathic macular telangiectasia

To characterize the electroretinographic response of the macula by multifocal electroretinography (mfERG) in patients with type 2 idiopathic macular telangiectasia (MacTel). A prospective study of mfERG in patients with type 2 MacTel was conducted from April 2009 to November 2009. mfERGs were recorded using a visual evoked response imaging system (MonElec2, Metrovision, Perenchies, France). The International Society for Clinical Electrophysiology of Vision (ISCEV) guidelines were followed. Patients with type 2 MacTel confirmed by fundus fluorescein angiography without subretinal neovascularisation were included. For recording purposes, 61 stimulus hexagonal elements were used. The first-order kernel mfERG responses were analyzed. Individual mfERG responses for the hexagons were grouped into concentric rings centered on the fovea for analysis (< 2, 5-10, 10-15 and >15°). Student's t-test and Mann-Whitney U test and linear regression analysis was performed with STATA ver 11.1 (StataCorp, College Station , TX, USA). Twenty eight eyes of 14 patients and 20 eyes of ten normal controls were included in the study. The mean logMAR visual acuity of the patients was 0.51 (Snellen equivalent 20/63). The mean N1 amplitude (nv/deg(2)) of patients were significantly reduced compared to controls and were as follows: 8.91 ± 14.00 vs 43.44 ± 9.55 (p < 0.0001) in less than 2°, 9.24 ± 10.47 vs 22.00 ± 3.87 (p < 0.0001) in 5-10°, 8.57 ± 10.02 vs 15.24 ± 1.89 (p < 0.0001) in 10-15°, and 7.03 ± 6.52 vs 12.47 ± 2.62 in > 15° (p < 0.001). The mean P1 amplitude (nv/deg(2)) was also significantly reduced in patients compared to controls and was as follows: 27.66 ± 37.44 vs 96.20 ± 12.41 (p < 0.0001) in less than 2°, 22.61 ± 19.38 vs 53.78 ± 9.79 (p < 0.0001) in 5-10°, 18.75 ± 20.21 vs 35.22 ± 4.16 (p < 0.001) in 10-15°, and 17.10 ± 12.54 vs 25.71 ± 3.93 (p < 0.001). The implicit time of N1 and P1 were also delayed significantly in all the rings. The mean central foveal thickness assessed by optical coherence tomography (OCT) scan was 84.78 ± 45.12μm. There was poor correlation between mfERG amplitudes or implicit times with either the visual acuity or OCT central thickness. mfERG showed significant reduction in amplitudes and implicit times of the waveforms in patients with type 2 MacTel in all the rings, suggesting a more generalized affection of the macula. The maximum reductions were seen in the <2(o) rings. Although there was poor correlation between the visual acuity and the amplitudes a of the waveforms, mfERG is a useful investigative modality for functional assessment of macula in type 2 MacTel patients.

Multifocal electroretinography amplitudes increase after photocoagulation in areas with increased retinal thickness and hard exudates

This study aimed to evaluate local response on multifocal electroretinography (mfERG) and to assess retinal thickness with optical coherence tomography (OCT) after focal laser treatment in areas with retinal oedema and exudates in patients with diabetic retinopathy. Twelve diabetes patients (aged 60 +/- 14 years, diabetes duration 16 +/- 8 years) treated with focal or grid photocoagulation in areas with retinal oedema and/or exudates underwent mfERG and OCT before and 3 months after treatment. The average thickness (in microm) in any of the nine sectors (defined according to the ETDRS) treated with photocoagulation was measured. Amplitudes and implicit times were analysed in corresponding areas on the mfERG. Mean mfERG amplitudes increased after photocoagulation (21.5 +/- 8.0 nV/deg(2) versus 16.8 +/- 6.1 nV/deg(2); p = 0.012), whereas no difference was seen in implicit times. Mean OCT values in the treated regions were lower at follow-up (272 +/- 23 microm versus 327 +/- 79 microm; p = 0.013). No correlation was seen between changes in mfERG response and changes in OCT values. The decrease in retinal thickness was correlated with the number of laser spots applied (p = 0.002). Focal argon laser treatment is effective in reducing retinal thickness. In addition, treated areas tend to show improved retinal function as demonstrated by increased amplitudes on mfERG.

Multifocal electroretinography in isolated arterially perfused bovine eye

To develop an isolated arterially perfused bovine eye as an in vitro model for studying retinal electrophysiology using multifocal electroretinography (mfERG). Fresh bovine eyes were cannulated through the ophthalmic artery and perfused with oxygenated Krebs' solution at 37 degrees C within 15 min postmortem. Multifocal ERG was recorded using the veris 1.0 (Visual Evoked Response Imaging System). The mfERG waveform of in vitro bovine eyes had a typical trough (negative wave, N1) and peak (positive wave, P1) similar to those of human mfERG. The implicit times (peak latencies) for N1 and P1 were 20 and 42 ms respectively, and the average response amplitude (N1P1) was 55 nV. The implicit times of N1 and P1 were maintained for more than 4 h. The mfERG responses were affected proportionately by the stimulus intensity. Without a neutral density filter, the mean response amplitude was about 55 nV, which was diminished to 26, 18 and 10 nV under neutral density filters of 0.4, 1.0 and 1.4, respectively. Partial occlusion of the pupil completely abolished mfERG responses from the corresponding part of the retina. Isolated arterially perfused bovine eye may be used as an experimental model to study retinal electrophysiology using mfERG. The in vitro eye may offer a convenient and easily obtainable alternative to live animals, particularly for drug screening and invasive studies.

Changes in the s-wave of multifocal electroretinograms in eyes with primary open-angle glaucoma.

To determine whether the s-wave is present in the multifocal electroretinogram (mfERG) and whether it is altered in eyes with primary open-angle glaucoma (POAG). A Visual Evoked Response Imaging System was used to record mfERGs from 15 eyes of 15 normal adults, as control eyes, and from 15 eyes of 15 patients with POAG. The stimulus consisted of 37 hexagonal stimulating elements with luminances of 200 cd/m(2) (white), 66.6 cd/m(2) (gray), and 4 cd/m(2) (black). The white or black element was presented at five different base periods (bpds) from 13.3 to 213.3 ms according to a binary m-sequence. In the intervals between the white and black (or white) elements, gray elements were inserted at 75 Hz. The changes in the amplitude and implicit time of the s-wave of the all-trace waveform of the first-order kernel of the mfERG were compared with the mean deviation (MD) of retinal sensitivity in the whole visual field measured with a Humphrey Field Analyzer. The s-wave was present as a positive wavelet on the descending limb of the first-order kernel response of the mfERGs of all eyes with POAG. The s-wave amplitude increased with prolongation of the bpd, as occurs in normal eyes. The mean amplitudes of the s-waves at bpds of 53.3 and 106.7 ms were significantly smaller in the eyes with POAG than in the control eyes. The correlation between the s-wave amplitude and the severity of disturbance in the entire visual field indicated by the MD was not significant in eyes with POAG. The characteristics of the s-wave in glaucomatous eyes were the same as those in the control eyes, but the amplitude of the s-waves in POAG eyes was significantly lower than that in the control eyes. This suggests that ganglion cells may be involved in the development of the s-wave. When comparing the s-wave with static perimetry, more local responses of the s-wave and more local retinal sensitivity in the static perimetry will be appropriate.

Multifocal magnetoencephalogram applied to objective visual field analysis.

To establish an objective visual field analysis by visual evoked magnetic fields. Forty-eight focal areas of the visual field were stimulated by the visual evoked response imaging system (VERIS). The multifocal visual evoked magnetic fields (mfVEFs) of 11 healthy subjects were recorded. The output signals were recorded with VERIS, and the second-order kernel was calculated. The equivalent current dipoles (ECDs) were estimated, and the relative positioning of ECDs was determined by a magnetoencephalography (MEG) system. The mfVEFs consisted of either two- or three-peak waves. Large amplitude mfVEFs were elicited when the stimulus was confined to 6 degrees of the central visual field, but a strong response could not always be obtained between 6 degrees and 12 degrees. All ECDs were estimated to originate in the occipital striate cortex. The ECDs for the upper (lower) field stimulations were estimated to be on the lower (upper) cortex, while those for right (left) field stimulations were on the left (right) cortex. The locations of mfVEF peak ECDs were correlated with the stimulated visual field and generally matched the cruciform model. In combination with the multifocal technique, MEG can be used for objective visual field analysis.

Multifocal electroretinogram in branch retinal vein occlusion

Purpose To describe the response from multifocal electroretinography in branch retinal vein occlusion. Design Prospective observational case control series. Methods Multifocal electroretinography was recorded in 15 patients with temporal branch retinal vein occlusion and 21 control subjects using a visual evoked response imaging system. Results There were significant differences in mean amplitude ( P = .01) and latency ( P = .001) between thrombotic and nonthrombotic retina in the same eyes, as well as in patients compared with control subjects. Conclusion Responses from multifocal electroretinography demonstrate retinal dysfunction in branch retinal vein occlusion; additional studies will demonstrate whether multifocal electroretinography has a prognostic value.

Preoperative and postoperative assessment by multifocal electroretinography in the management of optic disc pits with serous macular detachment

Purpose To evaluate the macular function by means of multifocal electroretinogram (MF ERG) in eyes with congenital optic disc pit and serous macular detachment. The evaluation was performed before and after the successful surgical intervention. Design Nonrandomized, comparative (self-controlled), interventional trial. Participants Ten patients (10 eyes) with optic disc pit with serous macular detachment were treated with the macular buckling procedure and followed up from March 1999 through May 2001. Methods In all patients included in the study, MF ERG was recorded before and after treatment. For recording, the VERIS III system (Visual Evoked Response Imaging System; Tomey, Nagoya, Japan) was used. Main outcome measures The retinal response densities were studied before and after treatment in areas 1 and 2 and were compared with visual acuity. Results The MF ERG before treatment showed decreased retinal response densities in all 10 cases. Twelve months after the surgical intervention, the electrical response densities in areas 1 (foveal area) and 2 (parafoveal area) improved. Further improvement was noted in 3 of the 10 patients who completed a follow-up of 18 months after treatment. In 8 of the 10 patients, postoperative visual acuity also increased. In the remaining two patients, visual acuity did not change after treatment, despite improvement of the retinal response densities. Conclusions In eyes with congenital optic disc pit with serous macular detachment, the decrease in retinal electrophysiologic response before treatment was not limited to the fovea, but also involved the perifoveal area. In all 10 eyes 12 months after treatment, the electrical activities in areas 1 and 2 improved. This improvement was not always followed by an increase in visual acuity. In 2 of the 10 patients, visual acuity remained unchanged. The values of retinal response densities before treatment cannot be used alone as a prognostic factor for the postoperative functional retinal results. It should also be stressed that the results of this study cannot be compared with the results of studies where spontaneous resolution of the macular detachment occurred.

Spatial Characteristics of the First-order Kernels of Multifocal Electroretinogram Waveforms with High-rate Sampling and Long-duration Recording

Detailed analysis of normal multifocal electroretinogram (mERG) first-order kernels in man. mERGs recorded repeatedly from a well-trained examinee were analyzed with a visual evoked response imaging system (VERIS). Sampling interval and recording duration were set to yield better resolution and lower S/N ratio. Reproducibility was tested in the "all trace" waveform. Focal variation of each of the 103 waveforms and regional variation of grouped waveforms were analyzed. The variation coefficient of the "all traces" waveform was lower for peak latencies than for response densities. Among the 103 focal waveforms, the response density was highest at the macular area and lowest around the optic nerve head. The central ring had the highest response density and the longest peak latency among concentric annular areas. Response density was higher in the upper or nasal retina than in the lower or temporal retina. The area with higher response density demonstrated a tendency to show longer peak latency. mERG response density was highest at the macular area and lowest around the optic nerve head. The N1 and P1 peak latencies were longest at the macular area and the N2 peak latency was longest around the optic nerve head.

Effects of Aging on the First and Second-order Kernels of Multifocal Electroretinogram

Purpose: To determine the effects of aging on the first and second-order kernels of the multifocal electroretinogram (ERG). Methods: Multifocal ERGs were recorded from 52 healthy subjects (52 eyes) (0 ≥ refractive error ≥ −3.0 diopter). The ages of the subjects ranged from 12–76 years with a mean (±SD) of 44.0 ± 20.2 years. The Visual Evoked Response Imaging System was used. The effects of aging on the response densities and on the implicit times of the first positive wave (P1) of the first-order kernel, and of the second and third positive waves (P2 and P3) of the second-order kernel were analyzed for the different age groups. Results: The response densities of the first-order kernel P1 and second-order kernel P2 waves decreased significantly, and the implicit times of the second-order kernel P2, and P3 were significantly prolonged ( P < .05) in subjects over 50 years of age. Conclusion: The results suggest that the age of the subject should be considered when evaluating retinal function using multifocal ERGs in basic and clinical studies.

Effects of Stimulus Intensity on Multifocal Electroretinograms

To investigate origins of responses of the second order kernel components of multifocal electroretinograms (m-ERGs), the influence of stimulus intensities on the waveform were studied. M-ERGs were recorded from 20 normal eyes of 14 normal adults using a Visual Evoked Response Imaging System with 19 hexagonal stimulus elements with light intensities of 6.3, 20, 63, 200, or 331 cd/m2. The response densities and implicit times of the first (N1, P1, N2) and the second order kernel components (P1, N1, P2, N2, P3, N3) of the m-ERGs were measured. The components were divided into two groups based on the behavior of the each component to the stimulus intensity change. The first group consisted of all the first order kernel components and P1 and N1 of the second order kernel components whose response densities were significantly larger (p < 0.05) than those of components elicited by stimulus of one grade lower intensity. The second group consisted of N2, P3, and N3 of the second order kernel components whose response densities did not increase when the stimulus intensity was increased from 200 to 331 cd/m2. It is probable that in the second order kernel components, the origin of P1, N1, and P2 is different from N2, P3, and N3 because the response to stimulus intensity of the two groups of components was different.

The Effects of Aging on the Multifocal Electroretinogram

Purpose: In order to use multifocal electroretinogram (m-ERG) for clinical assessment, we investigated the effects of aging on waves of the first and second order kernels of the m-ERG. Subjects and Methods: m-ERGs were recorded from 93 eyes (refractive error 0 to −3. 0 D) of 56 normal subjects (range, 12–79, mean, 44.2 ± 20. 7 years of age) using the Visual Evoked Response Imaging System (VERIS Science ®, version 3.0.1). We analyzed effects of aging on the response densities and the peak latencies of the first positive wave (P 1) of the first order kernel and the second and third positive waves (P 2 and P 3) of the second order kernel. Results: The response densities of the P 1 and P 2 waves significantly decreased, and the peak latencies of the P 1, P 2 and P 3 were significantly prolonged ( P < 0.05) in the subjects above 50 years old. Conclusion: The results suggested that the aging effect on the m-ERG should be considered when evaluating retinal function using m-ERGs in basic and clinical studies.

Multifocal electroretinography in retinitis pigmentosa

To investigate the diagnostic potential of multifocal electroretinography for the evaluation of retinal affection by retinitis pigmentosa in a clinical setting. For this prospective study, multifocal electroretinograms were obtained from 38 patients who matched the inclusion criteria of either a detectable photopic Ganzfeld response or visual fields of 10 degrees or more, and from 30 normal volunteers. Recordings were performed with the visual evoked response imaging system, using a resolution of 61 hexagonal elements within a 30-degree visual field. The results of the left eye of each patient and control subject were used for statistical evaluation by the Mann-Whitney U test. The 38 eligible patients included those with Usher syndrome types I and II (one patient and six patients, respectively) and those with autosomal-recessive (18), X-recessive (two), and autosomal-dominant (11) forms of retinitis pigmentosa. In 27 (71%) of these 38 patients, at least a central response of the multifocal electroretinogram was detectable. Loss of multifocal electroretinogram response density in patients with retinitis pigmentosa was significant (P < .00001) in all five eccentricity groups (concentric rings), with a progression from center to periphery. Implicit time was significantly elevated in the third eccentricity group (P < .0038) and increased further toward the periphery (P < .00001). The results did not differ notably between retinitis pigmentosa subgroups. Because the multifocal electroretinogram differentiates between affected and nonaffected retinal areas, eccentricity-dependent changes in both amplitude and implicit time were found. It can therefore add to the diagnostic information of many patients with retinitis pigmentosa.

The repeatability and variability of the multifocal electroretinogram for four different electrodes

Multifocal electroretinograms were recorded from twelve subjects on three separate days using the Visual Evoked Response Imaging System (VERIS). The subjects were 18–40 years-of-age. Each recording session was separated by an interval of between one and 16 weeks. Four electrode types were compared: the JET contact lens electrode, the gold foil electrode, the DTL thread electrode and the carbon fibre (c-glide) electrode. The b-wave amplitude density (nV/ sq.deg) recorded with each electrode was measured. The mean amplitude density recorded at each session for each subject and each electrode was calculated and compared. There were no significant differences in amplitude density for the ERGs recorded with each type of electrode over the three days. The coefficient of variation for each electrode and each subject was then calculated using the results for the three days. The coefficients of variation for each electrode showed significant differences (One-way ANOVA:F= 4.51, d.f. = 3, 44, P< 0.008). The c-glide electrode results had the highest variability and post hoc tests showed that its coefficient of variation was significantly different from those of the JET and gold foil electrodes but not from that of the DTL thread electrode.

The repeatability and variability of the multifocal electroretinogram for four different electrodes

Multifocal electroretinograms were recorded from twelve subjects on three separate days using the Visual Evoked Response Imaging System (VERIS). The subjects were 18-40 years-of-age. Each recording session was separated by an interval of between one and 16 weeks. Four electrode types were compared: the JET contact lens electrode, the gold foil electrode, the DTL thread electrode and the carbon fibre (c-glide) electrode. The b-wave amplitude density (nV/sq.deg) recorded with each electrode was measured. The mean amplitude density recorded at each session for each subject and each electrode was calculated and compared. There were no significant differences in amplitude density for the ERGs recorded with each type of electrode over the three days. The coefficient of variation for each electrode and each subject was then calculated using the results for the three days. The coefficients of variation for each electrode showed significant differences (One-way ANOVA: F = 4.51, d.f. = 3.44, P < 0.008). The c-glide electrode results had the highest variability and post hoc tests showed that its coefficient of variation was significantly different from those of the JET and gold foil electrodes but not from that of the DTL thread electrode.

Contrast and luminance as parameters defining the output of the VERIS topographical ERG

The Visual Evoked Response Imaging System (VERIS I) topographical electroretinogram system (EDI Associates, San Francisco, CA) allows measurement of the response of large numbers of retinal areas simultaneously. This paper examines ERG responses derived with the VERIS system to changes in target contrast and to local reductions in luminance. There is a linear reduction of response with reductions of target contrast. Neutral density filters were placed over part of the display, to mimic the localised reductions in response which occur in glaucoma, age-related maculopathy or diabetic retinopathy. There is a definite reduction in response seen with a 0.4 ND filter, indicating that the system should have similar sensitivity in detection of retinal lesions to the commonly used visual field analysis systems.