Relationship between transient and steady-state pattern electroretinograms: Theoretical and experimental assessment

CONCLUSIONS. The study shows that PERGSS results from the overlapping of tr PERGtr waveforms generated at that reversal rate. The first two peaks (N_SS and P_SS) of the PERG_SS reflect N35 and P50 waves of the tr PERG_tr. The N95 amplitude is reduced at conventional (16 rps) SS rates, but contributes to the overall PERG_SS amplitude.

PURPOSE. We determined if the overlap of transient (tr) pattern electroretinograms (PERGtr) can explain the generation of the steady-state (SS) pattern electroretinogram (PERGSS), and investigated the relationship between the two types of responses.

METHODS. Slightly jittered pattern reversals were used to generate quasi SS (QSS) PERGSS responses from eight normal subjects, recorded using lower eyelid skin electrodes, at rates between 6.9 and 26.5 reversals per second (rps). Jittered quasi PERGSS were deconvolved using the frequency domain continuous loop averaging deconvolution method. Additionally, conventional PERGtr at 2.2 rps and PERGSS at each of the QSS stimulation rates were obtained from all subjects. Two synthetic PERGSS responses were constructed at each stimulation rate, one using the PERGtr obtained at that rate, and the other using the conventional 2.2 rps PERGtr. Synthetic responses then were compared to the recorded PERGSS using amplitude, latency, and spectral measurements.

RESULTS. Findings indicate that the PERGSS obtained at SS rates can be predicted using the superposition of deconvolved tr PERGs at each particular rate. Although conventional PERGtr can explain PERGSS obtained at rates below 15.4 rps (≥97% correlation), for higher reversal rates only deconvolved responses obtained at that rate can produce the recorded SS responses (96% vs. 65% correlation at 26.5 rps).