Dataset Information

Measuring the Photopic Negative Response: Viability of Skin Electrodes and Variability Across Disease Severities in Glaucoma.

ABSTRACT:

Purpose

The purpose of this study was to determine the feasibility of measuring the photopic negative response (PhNR) of the full-field electroretinogram (ERG) using skin electrodes compared to conjunctival electrodes and its test-retest variability over a range of disease severities in open-angle glaucoma.

Methods

Recordings were performed twice (100 sweeps each) within the same session in 43 eyes of 23 participants with glaucoma to determine its intrinsic variability. The ratio between the PhNR and B-wave amplitude (PhNR/B ratio) was determined for each trace and computed across 5 to 100 sweeps of each recording. Spectral-domain optical coherence tomography was used to measure the average peripapillary retinal nerve fiber layer (RNFL) thickness.

Results

The PhNR/B ratio and its magnitude of variability were not significantly different between skin and conjunctival electrodes (P ? 0.197), and the degree of variability decreased substantially with increasing number of sweeps. For skin electrodes, the intraclass correlation coefficient was 0.89 and 0.91 for right and left eyes, respectively. The variability of the PhNR/B ratio decreased with lower RNFL thickness values and larger B-wave amplitudes (P ? 0.002).

Conclusions

Skin electrodes are a viable alternative to conjunctival electrodes when measuring the PhNR in open angle glaucoma, and increasing the number of sweeps substantially reduced its intrinsic variability; the extent of variability was also lower with worsening disease severity.

Translational relevance

The feasibility of performing ERG recordings widely across a range of disease severities in glaucoma can be achieved through using skin electrodes and increasing the number of sweeps performed to improve measurement repeatability.

SUBMITTER: Wu Z

PROVIDER: S-EPMC4795588 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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Publications

Measuring the Photopic Negative Response: Viability of Skin Electrodes and Variability Across Disease Severities in Glaucoma.

Wu Zhichao Z Hadoux Xavier X Fan Gaskin Jennifer C JC Sarossy Marc G MG Crowston Jonathan G JG

Translational vision science & technology 20160315 2

<h4>Purpose</h4>The purpose of this study was to determine the feasibility of measuring the photopic negative response (PhNR) of the full-field electroretinogram (ERG) using skin electrodes compared to conjunctival electrodes and its test-retest variability over a range of disease severities in open-angle glaucoma.<h4>Methods</h4>Recordings were performed twice (100 sweeps each) within the same session in 43 eyes of 23 participants with glaucoma to determine its intrinsic variability. The ratio ...[more]

PMID: 26998406

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Project description:PurposeTo evaluate the association between OCT-angiography (OCTA) and photopic negative response (PhNR) in open angle glaucoma (OAG) patients and assess the diagnostic accuracy of these parameters in early detection of glaucoma.MethodsA total of 152 eyes were enrolled in this study, 28 eyes with mild POAG (group I), 44 eyes with moderate-severe POAG (group 2) & 80 eyes of healthy subjects (control group). Full ophthalmological examination, OCTA and PhNR measurements were underwent for all participants. RNFL, GCC thicknesses, PhNR (implicit time and amplitude) were recorded. The superficial and deep capillary plexus vessel density (SCP-VD%, DCP-VD%) were measured by using 6 × 6 mm macula OCTA scans. The peripapillary vessel density (RPC-VD %) were measured by using 4.5 × 4.5 mm optic disk head OCTA scans.ResultsThere were reduction of the median Interquartile range (IQR) thickness of the GCC and RNFL in OAG eyes versus normal (P < 0.001). RPC-VD%, SCP-VD % and DCP-VD% were significantly reduced in OAG eyes versus normal (P < 0.001). Increased OAG severity was associated with more reduction in PhNR amplitude and increased implicit time. Reduced PhNR amplitude and prolonged latency were significantly correlated with reduced vascular parameters. The RCP-VD and PhNR amplitude demonstrated higher diagnostic accuracy (98.7) with the largest AUC and higher sensitivity and specificity (100% & 98.7%, respectively), followed by the PhNR implicit time with (AUC = 0.995) with a diagnostic accuracy 98.7. The SCP-VD, RNFL and GCC thickness had a diagnostic accuracy of (75.0, 81.6 & 84.2), respectively (P < 0.001).ConclusionsOCTA vascular parameters displayed significant positive correlation with PhNR amplitude and significant negative correlation with PhNR implicit time. OCTA and PhNR parameters showed a high diagnostic accuracy for detection of glaucoma, and both may provide promising insight in early detection of glaucoma. This study was retrospectively registered on ClinicalTrials.gov (identifier, NCT05104294).

Project description:PurposeTo compare measurements of the full-field photopic negative response (PhNR), as well as intra-subject variation in the PhNR, using time and time-frequency domain analyses.MethodsFull-field ERGs were recorded from 20 normally sighted subjects (aged 24-65 years) elicited by a long-wavelength pulse (3 cd s m-2) presented against a short-wavelength adapting field (12.5 cd m-2). Three to 10 waveforms were obtained from each subject, and each waveform was analyzed using standard time domain analyses of the PhNR, as well as a discrete wavelet transform (DWT) to extract time-frequency components that correspond to the PhNR. Three different measures of the PhNR were derived and compared: (1) amplitude at the PhNR trough; (2) amplitude at 72 ms following stimulus onset; (3) energy in the 11 Hz, 60-120 ms DWT frequency bin that corresponds to the PhNR. In addition, the effect of normalizing the PhNR by the b-wave was evaluated for each of the measures. Coefficients of variation (CVs) were computed for each definition to evaluate intra-subject variation.ResultsPhNR amplitudes measured at the trough and at 72 ms were significantly correlated (r = 0.88, p < 0.001). Additionally, PhNR energy derived by DWT was significantly correlated with the amplitude measured at the trough (r = 0.64, p = 0.002) and at 72 ms (r = 0.60, p = 0.005). Mean (±SD) intra-subject CVs were 26 % (15 %), 49 % (26 %), and 30 % (15 %), for measures at the trough, 72 ms, and DWT, respectively. Normalization by the b-wave amplitude (i.e., PhNR/b) had minimal effect on the intra-subject CVs, whereas normalization by the sum of the b-wave and PhNR amplitudes (i.e., PhNR/[b + PhNR]) substantially reduced the CVs for all three measures (mean CVs were less than 17 % for all conditions).ConclusionsAlthough each PhNR definition has advantages and disadvantages, all three metrics provide similar estimates of the PhNR. Intra-subject CVs, however, were relatively high for measurements made at 72 ms, indicating that definitions based on a fixed time point may introduce variability. The substantial decrease in intra-subject variation after normalization by the sum of the PhNR and b-wave amplitudes may be advantageous under some conditions.

Dataset Information

Measuring the Photopic Negative Response: Viability of Skin Electrodes and Variability Across Disease Severities in Glaucoma.

Purpose

Methods

Results

Conclusions

Translational relevance

Publications

Measuring the Photopic Negative Response: Viability of Skin Electrodes and Variability Across Disease Severities in Glaucoma.

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