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

Area of Science:

• Ophthalmology
• Neuroscience
• Visual Electrophysiology

Background:

• The pattern electroretinogram (PERG) is a key electrophysiological test used in ophthalmology.
• Distinguishing between transient (PERG(tr)) and steady-state (PERG(SS)) PERG responses is crucial for understanding retinal function.
• The relationship between PERG(tr) and PERG(SS) generation has not been fully elucidated.

Purpose of the Study:

• To determine if the overlap of transient PERG (PERG(tr)) waveforms can explain the generation of steady-state PERG (PERG(SS)).
• To investigate the relationship between PERG(tr) and PERG(SS) responses.
• To analyze how different stimulation rates affect PERG generation and waveform characteristics.

Main Methods:

• Quasi steady-state (QSS) PERG(SS) responses were recorded from normal subjects using slightly jittered pattern reversals at various rates (6.9–26.5 reversals per second).
• Jittered QSS PERG(SS) were deconvolved using frequency domain continuous loop averaging deconvolution.
• Conventional PERG(tr) and PERG(SS) were recorded, and synthetic PERG(SS) responses were constructed and compared to recorded data.

Main Results:

• The study found that PERG(SS) at steady-state rates can be predicted by the superposition of deconvolved PERG(tr) waveforms at each specific rate.
• Conventional PERG(tr) accurately predicted PERG(SS) below 15.4 reversals per second (≥ 97% correlation).
• At higher rates (e.g., 26.5 rps), only deconvolved PERG(tr) from that specific rate could accurately predict the recorded PERG(SS) (96% vs. 65% correlation).

Conclusions:

• PERG(SS) is indeed generated by the overlapping of PERG(tr) waveforms occurring at the same reversal rate.
• The initial peaks of PERG(SS) (N(SS) and P(SS)) correspond to the N35 and P50 waves of PERG(tr).
• While the N95 amplitude is reduced at conventional steady-state rates, it still contributes to the overall PERG(SS) amplitude.