APD-based rod cell model with integrated ion channel mechanisms for investigating the ERG a-wave and retinal diseases

Regulation of the electroretinogram (ERG) a-wave involves complex coupling between photocurrents and ion channel modulation, but the nonlinear functions in traditional mathematical models remain challenging to implement in biophysical frameworks. A novel biophysical model of rod cells based on avalanche photodiodes (APDs), with integrated ion channel mechanisms, is proposed to study the response characteristics of the ERG a-wave. The model successfully simulates photocurrents and photovoltage responses under different light stimuli. Based on the ERG a-wave, the constructed biophysical model of rod cells is used to analyze the typical waveform characteristics of two retinal diseases-Enhanced short-wavelength cone syndrome (ESCS) and Retinitis pigmentosa (RP). And the reliability of the model is verified by comparing the model output with published experimental results. This APD-based biophysical model overcomes the limitations of traditional ERG models, demonstrating the feasibility of using physical devices to characterize retinal phototransduction and ion channel mechanisms. Furthermore, it provides a pathway for clinical assessment of retinal diseases.