Time and frequency components of ERG responses in retinitis pigmentosa

PurposeTo evaluate the effects of retinitis pigmentosa (RP) on time, frequency, and time-frequency components of Xenon flash ERG signals using Fourier and wavelet transforms.MethodsXenon flash ERG was done in 18 eyes of nine RP patients and 20 normal eyes. After examining latency and amplitude, Fourier and wavelet transforms were performed using MATLAB software. Then, we extracted the mode frequency from the Fourier transform and main frequencies and their occurrence time from the wavelet transform. Finally, mean differences were analyzed using statistical tests.ResultsThe results indicated increased latency and reduced ERG wave amplitude, no significant inter-group difference in the average mode frequency, and significant reduction in main signal frequencies and their increased occurrence times. Also one or two of the three main frequencies had disappeared in more advanced cases.ConclusionRetinitis pigmentosa can induce changes in ERG time and time-frequency components. Impacted areas can be identified more accurately by wavelet transform and converting scales to frequencies.