Comparison between fullfield electroretinography obtained from handheld and tabletop devices in normal subjects

Objective: To compare full-field electroretinography (ERG) parameters obtained from Ephios handheld and VERIS tabletop ERG devices in normal subjects for interchangeable usability and reliability.

Design: Comparison study.

Participants: Comparison of full-field ERG between two devices for 57 normal subjects.

Methods: ERG was recorded for 57 normal subjects using tabletop device (VERIS 5.2.2X; Electro-Diagnostic Imaging Inc, San Mateo, Calif.) and handheld ERG device (Ephios handheld portable ERG system; ephios ab; Teknikringen, Linkoping, Sweden). Bland-Altman plot was done to measure the agreement between the 2 devices. Intraclass correlation coefficient (ICC) was calculated for amplitudes, implicit times, and b/a ratio to assess the reliability. Coefficient of variation (CV = 100 × [standard deviation/mean]) with 95% CI was calculated to measure the variability between the devices. Wilcoxon sign rank test was used to assess the repeatability of the Ephios handheld device.

Results: The mean a-wave and b-wave amplitudes of dark-adapted 3.0 ERG for the tabletop were 220.3 ± 52.6 and 471.5 ± 84.3 μV, respectively, whereas the mean a-wave and b-wave amplitudes in the same scotopic setting for the handheld device were 152.6 ± 34.2 and 379.7 ± 75.9 μV, respectively. The values represent mean ± standard deviation. The ICC of b/a ratio was 0.660 between the devices. The amplitudes CV of tabletop and handheld ERG devices ranged from 17.9% to 29.1% and from 22.4% to 30.1%, respectively.

Conclusions: The pattern of waveform of the Ephios handheld device is similar to the VERIS tabletop device. The ERG parameters showed variability between the 2 devices. Hence Ephios handheld ERG device can be used along with its normative data for measuring ERG. Because of variability, the devices cannot be used interchangeably.