Comparison of performance and patient satisfaction of two types of ERG electrodes

Effects of DTL electrode position on the amplitude and implicit time of the electroretinogram

PURPOSE

This study sought to investigate whether there is an optimal position of the Dawson, Trick, and Litzkow (DTL) electrodes when measuring the full-field electroretinogram (ERG) for monitoring purposes.

METHODS

In 200 uveitis patients, an extended light-adapted (LA) ERG protocol was measured twice, incorporating the International Society for Clinical Electrophysiology of Vision standards. First, a LA ERG was measured with the DTL in the lower lid position (LLP) and thereafter in the fornix position. Differences in amplitudes and implicit times of a-waves, b-waves, and the 30 Hz peak were investigated. Intraclass correlation coefficients (ICCs) as well as coefficients of variation (CoV) were calculated, to assess both reliability and relative variability between the two DTL positions.

RESULTS

Implicit times showed no statistically significant differences between the two DTL positions. As expected, amplitudes at the different stimulus strengths were 1.12-1.19 higher in the LLP, but there were no significant differences in the CoV between the two DTL positions. The ICC was high for the b-wave and 30 Hz flicker response (0.842-0.979), but lower for the a-wave, especially for amplitudes (0.584-0.716).

CONCLUSIONS

For monitoring purposes in patients, we conclude that based on relative variability, no position is preferable above the other. However, because in most diseases amplitudes are decreased, the LLP may be chosen because it yields higher amplitudes. Whatever the choice, it is important to ensure that the DTL position remains stable during an ERG recording.

Prolonged Cone b-Wave on Electroretinography Is Associated with Severity of Inflammation in Noninfectious Uveitis

PURPOSE

This study sought to investigate retinal function in patients with noninfectious uveitis by using full-field electroretinography (ERG) and correlate the ERG to disease duration and severity of inflammation.

DESIGN

Prospective cohort study.

METHODS

Patients (n = 200) with noninfectious uveitis and a disease duration of <1 year (group A [n = 80]) and those with a disease duration of >5 years (group B [n = 120]) were included. ERGs of the total 355 uveitis eyes were measured according to an extended International Society for Clinical Electrophysiology of Vision protocol. ERG abnormalities were related to demographics and uveitis characteristics, including anatomical classification, duration of uveitis, severity of inflammation, best corrected visual acuity (BCVA), cystoid macular edema (CME), and the highest fluorescein angiography (FA) score during the course of the disease.

RESULTS

ERGs showed abnormalities in 235 eyes (66.2%). The most frequent and pronounced ERG abnormality was a prolonged implicit time of the cone b-wave (151 eyes [42.5%]), which was associated with vitritis (P = .005); cells in the anterior chamber (P = .007); the highest fluorescein angiography score (P = .011); age (P < 0.001); and pupil diameter (P < 0.001). BCVA was relatively good (0.05 logMAR [interquartile range {IQR}, 0.011, 0.22]) and not associated with this ERG abnormality. There were no differences between the ERG abnormalities in group A and those in group B and no significant associations between ERG abnormalities and anatomical classification or specific diagnoses.

CONCLUSIONS

ERG results are frequently affected in cases of noninfectious uveitis of all anatomic subtypes, including anterior uveitis without apparent inflammation of the posterior segment. ERG abnormalities appear to be associated with the severity of inflammation from both the present and the past and therefore may be seen even when signs of retinal inflammation have disappeared.

Electroretinograms recorded with skin electrodes in silicone oil-filled eyes

Purpose

To assess the physiology of the retina by electroretinography (ERG) with skin electrodes in eyes that had undergone vitrectomy with silicone oil (SO) tamponade.

Design

Retrospective case series.

Method

ERGs were recorded from eleven eyes with complex vitreoretinal disorders and from the normal fellow eyes. The affected eyes underwent pars plana vitrectomy (PPV) with SO tamponade. ERGs were recorded before and after the SO was removed. The amplitudes and implicit times of the a- and b-waves of the affected eyes were compared to those of the normal fellow eyes. In addition, the ratios of the amplitudes of the b-waves of the affected eyes to those of the fellow eyes were compared before and after the SO was removed.

Results

ERGs were recordable from 7 eyes (63.6%) before the SO was removed and 11 eyes (100%) after the SO was removed. The a- and b-wave amplitudes were significantly smaller in the affected eyes than those of the fellow eyes at the baseline. The b-wave amplitude before the removal of the SO was significantly and positively correlated with that after the SO removal. The ratios of the b-waves of the affected/normal fellow eye significantly increased after the SO was removed.

Conclusion

The results indicate that ERGs picked up by skin electrode can be used to assess the physiology of the retina in eyes with a SO tamponade. The amplitude of the b-waves of the ERGs in silicone-filled eyes can be used to predict the amplitude after the silicone is removed.

The DTL ERG electrode comes in different shapes and sizes: Are they all good?

PURPOSE

Although the DTL fiber electrode has been in use in the ERG field for more than four decades, its composition was never clearly defined. We compared five different types of conductive (DTL type) yarn (differing in terms of mass, number of filaments, and crimping degree) in order to determine whether we could identify one that would be better suited for the recording of ERGs.

METHODS

Photopic flash ERGs were recorded from five subjects using the following DTL electrodes: 27/7, 22/1, 11/1, 11/1*2, and 22/1*2. Data analysis included amplitude and peak time measurements of the a- and b-waves in the time domain (TD) as well as measurements of specific frequency descriptors of the ERG waveform in the time-frequency domain using the discrete wavelet transform (DWT) approach. The degree of comfortableness was also assessed in 12 subjects with two surveys (Likert 5-point and the ranking scale).

RESULTS

Comparisons of TD and DWT parameters did not permit to identify the best DTL electrode, all yielding comparable measures. There was a slight trend for the largest electrode (22/1*2) to yield the largest response, but this was at the expense of comfort, the 22/1*2 electrode being rated as the least comfortable.

CONCLUSIONS

Given the minimal impact the different electrodes had on the amplitude of the signal, we believe that comfort should dictate our choice. It would appear from our results that use of a multifilament electrode is the best choice since one can get an electrode whose size is optimized for the recording of large responses while minimizing the foreign-body sensation due to the small size of each of the filaments that compose this multifilament electrode.

Variability of the multifocal electroretinogram based on the type and position of the electrode

PURPOSE

To evaluate and compare the wave amplitude of multifocal electroretinogram (mfERG) measurements and discomfort from Dawson-Trick-Litzkow (DTL) electrode located on the cornea (cDTL) and on the conjunctival fornix (fDTL) and ERG-jet contact lens electrode (CL).

METHODS

Thirty-six patients and 18 healthy volunteers were evaluated with three different methods (cDTL, fDTL and CL). Wave amplitude, number of artifacts, number of electrode dislocations and level of discomfort obtained with each electrode were compared. These variables were also compared between patients and healthy volunteers (control group). Comparisons between wave amplitudes were made using intraclass correlation coefficient (ICC).

RESULTS

Responses by the three tested electrode were better correlated (ICC) in patient (0.616-0.756) than in control groups (0.342-0.679). CL provided the highest wave amplitude in both groups (p < 0.005), but it was associated with higher discomfort (p < 0.001) and the highest rate of dislocations (72 and 100 % in control and patients, respectively). Looking at the differences obtained by each electrode between both groups, CL seems to be able to differentiate patient from control in the ring 1 of the mfERG. By contrast, fDTL gave the lowest wave amplitude in both groups, but it had the advantage to, apparently, discriminate between patients and control group in rings 1 and 2. cDTL produced more artifacts than the other electrodes in both groups (p < 0.001).

CONCLUSIONS

Although wave amplitude measurements with different electrodes were correlated, they cannot be directly compared, so it is mandatory to create an appropriate normative database with each electrode. Despite providing the lowest amplitudes, fDTL seems to offer the best features to perform mfERG regarding discomfort, number of artifacts and diagnostic capability.

Comparing DTL microfiber and Neuroline skin electrode in the Mini Ganzfeld ERG

BACKGROUND

In infant ERG recordings skin electrodes frequently result in a better compliance. In order to assess the quality of such recordings, we compared the recording characteristics of DTL microfiber and Neuroline surface electrodes using a modified ISCEV protocol in the Mini Ganzfeld ERG.

METHODS

A prospective cohort study on healthy adult subjects was conducted at the Department of Ophthalmology, University of Basel, Switzerland. Thirty healthy volunteers were tested. The microfiber electrode (DTL Plus Electrode) was placed across the cornea, above the lower eyelid. The Neuroline skin electrode was placed on the surface of the lower lid on the opposite eye. The eye on which each electrode type was placed was randomised. Amplitudes of the rod, standard combined, standard flash cone, light-adapted 3.0 Hz flicker and red cone responses were analysed, as well as their respective implicit times.

RESULTS

Both electrode recordings showed the same waveform characteristics. Responses with the Neuroline electrode were significantly weaker than those from the DTL electrode. Amplitudes of the rod, standard combined, standard flash cone, light-adapted 3.0 Hz flicker and red cone responses were up to four times larger when recorded with the DTL electrode (p < 0.005, ANOVA). Implicit times of the red cone ERGs were slightly faster for the Neuroline skin electrode recordings (p ≤ 0.039).

CONCLUSIONS

Comparison of full-field ERG recordings with microfiber DTL and Neuroline skin electrodes showed that DTL electrodes produce larger ERGs. Hence, we provide evidence that both electrode types allow successful full-field ERG recording, although separate normative data for both electrodes are necessary.

The effect of nutritional supplementation on the multifocal electroretinogram in healthy eyes

BACKGROUND

Previous studies have demonstrated an increase in macular pigment optical density (MPOD) with lutein (L)-based supplementation in healthy eyes. However, not all studies have assessed whether this increase in MPOD is associated with changes to other measures of retinal function such as the multifocal ERG (mfERG). Some studies also fail to report dietary levels of L and zeaxanthin (Z). Because of the associations between increased levels of L and Z, and reduced risk of AMD, this study was designed to assess the effects of L-based supplementation on mfERG amplitudes and latencies in healthy eyes.

METHODS

Multifocal ERG amplitudes, visual acuity, contrast sensitivity, MPOD and dietary levels of L and Z were assessed in this longitudinal, randomized clinical trial. Fifty-two healthy eyes from 52 participants were randomly allocated to receive a L-based supplement (treated group), or no supplement (non-treated group).

RESULTS

There were 25 subjects aged 18-77 (mean age ± SD; 48 ± 17) in the treated group and 27 subjects aged 21-69 (mean age ± SD; 43 ± 16) in the non-treated group. All participants attended for three visits: visit one at baseline, visit two at 20 weeks and visit three at 40 weeks. A statistically significant increase in MPOD (F = 17.0, p ≤ 0.001) and shortening of mfERG ring 2 P1 latency (F = 3.69, p = 0.04) was seen in the treated group.

CONCLUSIONS

Although the results were not clinically significant, the reported trend for improvement in MPOD and mfERG outcomes warrants further investigation.

Atypical pattern of rod electroretinogram modulation by recent light history: a possible biomarker of seasonal affective disorder

Our goal was to challenge both normal controls and patients with seasonal affective disorders (SAD) to various light histories and then measure their retinal response modulation using the electroretinogram (ERG) in both winter and summer. In winter and summer, 11 normal controls and 12 SAD patients were exposed to three different light conditions for 1 h (10,000, 100 and 5 lux) followed by an ERG. Groups showed similar ERG amplitudes in the 100 lux condition. Compared with the 100-lux condition, in controls, the ERG response was significantly increased in the 5-lux condition; in SAD, it was significantly decreased in the 10,000-lux condition. This pattern was present in both seasons. This is the first time a retinal response modulation anomaly has been observed in SAD patients in both the depressed and euthymic states. Retinal response modulation may represent an interesting biomarker of the disease for future research.

Inter-subject, inter-ocular and inter-session repeatability of the photopic negative response of the electroretinogram recorded using DTL and skin electrodes

The photopic negative response (PhNR) has attracted interest as a flash ERG component reflecting inner retinal activity, with investigators adopting various approaches to analysing the response. This study has two principal aims: first to determine the most reliable technique for assessing the PhNR amplitude; secondly to compare the repeatability characteristics of the PhNR recorded using DTL and skin active electrodes. Electroretinograms were recorded in 31 subjects, using both electrode types, in response to a Ganzfeld red stimulus (Lee filter "bright red"; 1.76 log phot td.s; 4 Hz) presented over a steady blue background (Schott glass filter BG28; 3.9 log scot td). Sixteen subjects returned to assess repeatability. PhNR amplitude was measured from b-wave peak-to-PhNR trough, pre-stimulus baseline to trough, and from peak and baseline to a fixed time-point; a ratio of b-wave/PhNR amplitude was also calculated. Coefficients of variation (CoV), and inter-ocular and inter-session limits of agreement (LoA) were calculated for all measures. The ratio of b-wave/PhNR amplitude showed the lowest CoV (14.3% DTL; 23.2% skin), inter-ocular LoA (22.2% DTL; 25.0% skin), and inter-session LoA (22.8% DTL; 20.3% skin). The peak-to-trough and peak-to-fixed-time measurements were also consistently reliable. Least reliable measures were those measured from baseline. While skin electrode responses were significantly smaller than DTL responses (P < 0.0001), the variability was only slightly increased. This study suggests that peak-to-trough measurements are the most reliable means of measuring the PhNR and ratio calculation further improves repeatability. Skin electrodes provided a viable alternative to DTL electrodes for recording the PhNR.