Oscillatory potentials as predictors to amplitude and peak time of the photopic b-wave of the human electroretinogram

Abstract

The oscillatory potentials are viewed by many as small oscillations of a high-frequency domain that ride on the b-wave of the electroretinogram. A study of electroretinograms and oscillatory potentials performed in 25 normal subjects was undertaken to substantiate my claim that oscillatory potentials are fast retinal potentials that are integrated to form the b-wave. The prominence of the OPs on the ascending limb of the b-wave was found to be only weakly correlated (r = -0.37) to the amplitude of the oscillatory potentials (measured in the 100-1000 Hz recordings). There was, however, a high correlation (r = 0.78) between the prominence of the oscillatory potentials and their frequency domain as determined by the peak-to-peak timing. Furthermore, the peak-to-peak timing of the oscillatory potentials was highly correlated with the b-wave peak time (r = 0.86) as well as with the 'a-wave trough to b-wave peak' time (r = 0.90), while the amplitude of the oscillatory potentials was correlated to the amplitude of the b-wave (r = 0.78). Interestingly, when combining the amplitude of the oscillatory potentials with the time interval between oscillatory potentials 2 and 3 and 3 and 4, a higher correlation (r = 0.88) was found with the b-wave amplitude. The latter finding would support my claim that the b-wave represents an integration (amplitude as a function of time) of the oscillatory potentials.

Oscillatory potentials and the b-Wave: Partial masking and interdependence in dark adaptation and diabetes in the rat

“…In addition, as has been previously mentioned, the OPs seem to contribute to the bwave's overall amplitude during the upstroke, as suggested by the results in the first part of this investigation and findings reported by others [19,20]. Hence, the loss of OP amplitudes is likely to have a direct effect on the measured height of the b-wave and account for much but not all of the decrease in the amplitude of the b-wave noted here.…”

“…This is further supported by the parallel finding that the total OP amplitude is related to bwave amplitude in a linear fashion across the period of dark adaptation tested here. This concept is supported by the work of Lachapelle, who demonstrated the contribution of individual OPs to the b-wave amplitude [19,20]. Interestingly, the empirical correlation between total OP amplitude and b- Fig.…”

“…Indeed, it is likely that the isolated OPs do represent at least some of the physiological events traditionally associated with the b-wave. Lachapelle et al have shown that the OPs are major contributors to the formation of the b-wave [19,20], and other studies have demonstrated a correlation between stimulus intensity and individual and combined OP amplitudes [4, 13, 21] similar Graefe's Arch Clin Exp Ophthalmol (2007) 245:1335-1345 …”

Asymmetrical growth of the photopic hill during the light adaptation effect

“…These results agree with previous findings that showed a more pronounced LAE for OP 4 compared to OP 2 and OP3 [1,4,5,12]. Of interest, the timing of photopic OP 4 was previously shown to be concomitant with the peak of the photopic b-wave [1,28,29], and time-locked to a segment of the photopic ERG response that included remnants of the OFF response evoked by longer flashes [30,31], thus suggesting that the retinal pathways leading to the OFF ERG response could explain most of the LAE. Supportive of the latter claim, Hamilton et al [21] showed that the photopic LR function from a patient affected with complete congenital stationary night …”

Advance in ERG Analysis: From Peak Time and Amplitude to Frequency, Power, and Energy

“…These components, referred to as oscillatory potentials (OPs), are most probably generated by the retinal cells of the inner retina (i.e., bipolar, amacrine, or horizontal cells) although their exact origin remains debated [8, 9]. The OPs appear to be major contributors to the shaping of the ERG waveform [10] and there is an abundant literature attesting to the clinical value of including the OPs when analyzing pathological ERGs [6, 11, 12]. Unfortunately, in order to optimize the visualization of the OPs one must modify the recording bandwidth of the ERG from a broadband (e.g., 1–1000 Hz) to a narrower band (e.g., 100–1000 Hz) that removes the low-frequency components of the ERG (i.e., a- and b-waves) and consequently selectively enhances the high-frequency components (i.e., OPs) [2].…”