Comparing the Variation of Time and Frequency Components of Electroretinogram in Patients with Retinitis Pigmentosa and Healthy Individuals

Background and Retinitis Pigmentosa (RP) is one of the retinal degeneration diseases affecting the eye signals. Electroretinogram (ERG) is a signal that plays an important role in diagnosis and treatment of RP. This signal includes useful information that cannot be revealed just in time domain. We aimed to investigate the effect of RP on time, frequency, and time-frequency parameters of ERG using the Fourier and wavelet transform processing methods.
In this experimental study Flash Xenon ERG was recorded from 18 eyes of RP patients and 20 eyes of healthy individuals. After extracting the latency and amplitude of the ERG signals, the Fourier and wavelet transforms were performed on the signals by MATLAB software. Then, the frequency mode and main frequencies along with the occurring time constituting the ERG signals were extracted. Finally, the differences between the means of all parameters were analyzed.
Findings indicated an increase in the latency and a decrease in amplitude of the ERG. But, no significant difference was found between the mean frequency mode of the RP patients and healthy individuals. A significant decrease was observed in the main constituent frequencies of the ERG signals and their occurrence time. In addition, with further development of the disease in the RP patients, one or two main frequencies were omitted.
RP disease can cause variations in time and time-frequency components of the ERG signals. By applying the wavelet transform on the ERG signals of the RP patients to convert their indices into frequency domain, the position of the retina affected mainly by this disease can be found.