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

Evaluation of correlation between Diopsys® NOVA™ fixed-luminance flicker ERG and Diagnosys® Espion 2™ flicker ERG parameters

PURPOSE

Diopsys® NOVA™ is a novel full-field electroretinography (ffERG) device that can make rapid measurements of retinal electrophysiologic function. Diagnosys® Espion 2™ is a clinical gold-standard ERG device. This study aimed to investigate whether light-adapted Diopsys® NOVA™ fixed-luminance flicker ffERG magnitude and implicit time (converted from phase) measurements correlate with light-adapted Diagnosys® Espion 2™ flicker ffERG amplitude and implicit time measurements, respectively.

METHODS

Twelve patients (22 eyes) with various retinal and uveitic diseases underwent light-adapted Diagnosys® Espion 2™ and Diopsys® NOVA™ fixed-luminance flicker testing. Diopsys® magnitude and implicit time (converted from phase) measurements were compared to Diagnosys® amplitude and implicit time measurements, and a Pearson correlation was used to evaluate any existing correlation. Groups were also compared using generalized estimating equations. Bland-Altman plots were utilized to determine agreement between the comparison groups.

RESULTS

Age of patients ranged from 14 to 87 years. 58% (n = 7/12) of patients were female. A significant, positive correlation (r = 0.880, P < 0.001) was observed between magnitude (Diopsys®) and amplitude (Diagnosys®) measurements. Amplitude increases by 6.69 µV for each 1 µV increase in Magnitude (p-value < 0.001). A statistically significant, strong positive correlation was observed between Diopsys® implicit time measurements (converted from phase) and Diagnosys® implicit time measurements (r = 0.814, p-value < 0.001). For each 1 ms increase in Diopsys® implicit time, Diagnosys® implicit time increases by 1.13 ms (p-value < 0.001).

CONCLUSIONS

There is a statistically significant positive correlation between light-adapted Diopsys® NOVA™ fixed-luminance flicker amplitude and Diagnosys® flicker magnitude values. Additionally, there is a statistically significant positive correlation between Diopsys® NOVA™ fixed-luminance flicker implicit time (converted from phase) and Diagnosys® flicker implicit time values. These results imply that the Diopsys® NOVA™ module, which utilizes the nonstandard shortened International Society for Clinical Electrophysiology of Vision (ISCEV) ERG protocol, can produce reliable light-adapted flicker ffERG measurements.

Comparison of DTL and gold cup skin electrodes for recordings of the multifocal electroretinogram

OBJECTIVE

To compare mfERG recordings with the Dawson-Trick-Litzkow (DTL) and gold cup skin electrode in healthy young and old adults and to test the sensitivity of both electrodes to age-related changes in the responses.

METHODS

Twenty participants aged 20-27 years ("young") and 20 participants aged 60-75 ("old") with a visual acuity of ≤ 0 logMAR were included. The mfERG responses were recorded simultaneously using DTL and skin electrodes. P1 amplitudes, peak times and signal-to-noise ratios (SNRs) were compared between both electrodes and across age groups, and correlation analyses were performed. The electrode's performance in discriminating between age groups was assessed via area under curve (AUC) of receiver operating characteristics.

RESULTS

Both electrodes reflected the typical waveform of mfERG recordings. For the skin electrode, however, P1 amplitudes were significantly reduced (p < 0.001; reduction by over 70%), P1 peak times were significantly shorter (p < 0.001; by approx. 1.5 ms), and SNRs were reduced [(p < 0.001; logSNR ± SEM DTL young (old) vs gold cup: 0.79 ± 0.13 (0.71 ± 0.15) vs 0.37 ± 0.15 (0.34 ± 0.13)]. All mfERG components showed strong significant correlations (R² ≥ 0.253, p < 0.001) between both electrodes for all eccentricities. Both electrodes allowed for the identification of age-related P1 changes, i.e., P1-amplitude reduction and peak-time delay in the older group. There was a trend to higher AUC for the DTL electrode to delineate these differences between age groups, which, however, failed to reach statistical significance.

CONCLUSIONS

Both electrode types enable successful mfERG recordings. However, in compliant patients, the use of the DTL electrode appears preferable due to the larger amplitudes, higher signal-to-noise ratio and its better reflection of physiological changes, i.e., age effects. Nevertheless, skin electrodes appear a viable alternative for mfERG recordings in patients in whom the use of corneal electrodes is precluded, e.g., children and disabled patients.

Qualitative and quantitative comparison of ERGs with contact lens and adhesive skin electrodes

PURPOSE

Traditional ERGs recorded using corneal electrodes can be difficult for some patients to tolerate. In the last several years, adhesive skin electrodes have gained in acceptance. In this report we present a qualitative comparison of waveforms as well as a quantitative analysis of correlation of amplitudes and implicit times of simultaneous ERG recordings using contact lens and skin electrodes.

METHODS

89 subjects were included; all were referred for full-field ERG testing for multiple indications. ERGs (obtained according to ISCEV standards) were recorded simultaneously from both eyes with ERG-jet corneal contact lens electrodes and LKC Technologies Sensor Strip adhesive skin electrodes using multi-channel instrumentation (Diagnosys LLC, Espion3). Waveforms, a-wave and b-wave amplitudes and implicit times were compared.

RESULTS

Waveform morphologies were similar between electrode types. Regression coefficients (conversion factors) for a-wave and b-wave amplitudes under both photopic and scotopic conditions were tightly clustered. Regression coefficients for implicit times were nearly equal to 1.0. The regression coefficient for the entire amplitude dataset was 0.349, with an overall correlation of 0. 869 between amplitude recorded with skin and contact lens electrodes. The regression coefficient for the entire implicit time dataset was 0.967, with an overall correlation of 0.964 between skin and contact lens electrodes.

CONCLUSIONS

Our best estimate for the conversion factor between ERG amplitudes recorded with adhesive skin electrodes and contact lens electrodes is 0.349-amplitudes with skin electrodes are about 1/3 the amplitudes recorded simultaneously from the same eyes with contact lens electrodes, with a high correlation. Implicit times are nearly identical for the two electrode types.

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.

Comparison of electroretinographic measurements between tabletop and handheld stimulators in healthy subjects

PURPOSE

To compare full-field electroretinography (ffERG) parameters obtained from handheld and tabletop electroretinography (ERG) devices in normal subjects.

METHODS

Twenty volunteers underwent ffERG using a tabletop and handheld stimulator. The responses obtained from the right eyes were compared. The coefficient of variation and intraclass correlation coefficient (ICC) were derived to assess inter- and intra-individual reliability.

RESULTS

The b-wave in the rod response, a- and b-waves in the maximal combined response, a-wave in the cone response, and the 30-Hz flicker response showed significantly greater amplitudes when recorded with the tabletop stimulator than with the handheld stimulator. The implicit time of response (ITR) in the 30-Hz flicker response was longer when recorded with the handheld stimulator than when recorded with the tabletop stimulator. With regard to amplitude, the ICC indicated moderate-to-high reliability in the measurement of the b-wave in the rod response, and a- and b-waves in the maximal combined response. With regard to ITR, measurement of the b-wave in the rod response and a-wave in the maximal combined response showed moderate-to-high reliability.

CONCLUSION

Despite the significantly lower ERG amplitude measurements recorded by the handheld stimulator, there were no significant differences in variability between the two stimulators.