Application of a Mapping Method in the Analysis of Electroretinogram in Patients with Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a group of degenerative retinal diseases characterized by mutations in genes affecting retinal pigment epithelium (RPE) function, as well as mutations directly involving photoreceptors. This paper aims to evaluate a nonlinear method to distinguish between the RP and normal eye based on the Electroretinogram (ERG) signal.

ERG signal was recorded from 28 eyes of patients with the RP and 32 normal eyes. The ERG signal consists of four different stimuli, including two dark-adapted and two light-adapted stimuli. The time-domain analysis includes the amplitude and implicit time to consider the robustness of the nonlinear method. A parabolic mapping method was performed, and two criteria (Theta angle and density) extracted from the parabola were compared for both groups.

The results showed that a-wave's amplitude and implicit time significantly changed in the dark- and light-adapted stimuli. The amplitude of the b-wave showed significant changes in all stimuli. However, the implicit time of b-wave had a significant increase only in the dark-adapted 3.0 ERG. Both nonlinear criteria showed significant changes in the RP group for all the stimuli. The p-values of dark-adapted 3.0 (p = .0121), dark-adapted 10.0 (p = .0014), light-adapted 3.0 (p = .0119), and flicker 30 Hz (p = .0323) showed significant differences. Using the density criterion, the statistical test demonstrated a significant difference between the RP and healthy normal group in dark-adapted 3.0 (p = .0076), dark-adapted 10.0 (p = .0024), light-adapted 3.0 (p = .0021), and flicker 30 Hz (p = .0165).

The proposed features have made it possible to distinguish between healthy and RP eyes. This method might be helpful in early diagnosis.