Investigating the frequency characteristics of the electroretinogram signal in patients with central retinal vein occlusion

Background: Central retinal vein occlusion (CRVO) is the second most common retinal vascular disorder after diabetic retinopathy. In this study, we tried to examine the potentials of time-frequency methods for differentiating the eyes with CRVO. Materials and methods: Twenty patients with unilateral CRVO were included in this study. Their contralateral normal eyes were considered as the control group. Two methods of Short-time Fourier transform (STFT) and Discrete Wavelet Transform (DWT) were implemented to determine the frequency components of the electroretinogram (ERG) signals which were recorded based on light-adapted 3 ERG and light-adapted 30 Hz flicker ERG.   Results: In the DWT method, the ERG response of light-adapted 3 ERG included three main components that corresponded to the advent of a, b, and i waves. Light-adapted 30 Hz flicker ERG included two main components that coincided with a and b waves. The first and second dominant frequencies of both ERGs in the CRVO and healthy groups showed a significant differentiation, and the time of the emerging frequency of the dominant frequency in the stimulation of irradiance increased by 3 cd.s.m-2. Conclusion: The DWT has shown the ability to distinguish between the frequencies of the eyes with CRVO and the healthy ones. The drop in frequency and latency of the predominant frequencies in light-adapted 3 cd.s.m-2 indicate a greater involvement of rod cells compared to the retinal cone cells.