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Yukako Inoue, Kei Kato, Kumiko Ishikawa, Makoto Nakamura; Mid-term fluctuations in the global indices of multifocal visual evoked potentials and Humphrey visual fields in controls and glaucomatous eyes.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):334.
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We have previously reported that the degree of signal-to-noise ratio (SNR) distribution overlap between a signal window and a noise window in multifocal visual evoked potential (mfVEP) responses, which is determined by the area under the receiver-operating characteristic curve (SNR-AUC), can quantitatively detect glaucomatous visual functional damage (Nakamura et al. Doc Ophthalmol, 2011). The purpose of this study was to compare mid-term fluctuations in the SNR-AUCs between eyes with primary open angle glaucoma (POAG) and control eyes.
We enrolled 30 eyes in 30 ophthalmologically normal controls and 37 eyes in 37 POAG patients whose mean deviations (MDs) in the Humphrey visual field (HVF) 24-2 were -15 dB or better. MfVEPs were recorded using 2 vertical channels and 1 horizontal channel as reported. The SNR-AUCs were calculated based on the root mean square amplitudes of the signal and noise windows. The HVFs and mfVEPs in the same individuals were recorded three times at different visits, and the coefficients of variation (CV) of the MDs, pattern standard deviations (PSDs), and SNR-AUCs were obtained. The MDs, PSDs, and SNR-AUCs from the three visits were compared using repeated measures of analysis of variance, and the logarithmic CVs of each parameter were compared using t-tests between the control and POAG eyes. Linear regression analyses were performed on the logarithmic CVs of the SNR-AUCs against the SNR-AUCs themselves.
The average (standard deviation) of the SNR-AUC and its CV were 0.97±0.02 and 0.012±0.008, respectively, in the control eyes and 0.87±0.09 and 0.040±0.037, respectively, in the POAG eyes. The SNR-AUC in the POAG eyes was significantly lower and its CV was significantly greater compared with the controls (P<0.0001). The MD at the third visit was significantly improved compared with the first visit in the controls, whereas the PSD was significantly worsened in the POAG eyes over the same time span. There were no significant fluctuations in the SNR-AUCs in both the control and POAG eyes. In the POAG eyes, the SNR-AUC CV improved as the MD (R2=0.28, P=0.0007), PSD (R2=0.26, P=0.0013), and SNR-AUC (R2=0.35, P=0.0001) worsened.
The SNR-AUC of the mfVEP showed high reproducibility in the control eyes, whereas its CV increased in a disease stage-dependent fashion in the POAG eyes.
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