Novel system for detection of pattern reversal visual evoked potentials

Objective: The purpose of this work is to create a portable and low-cost diagnostic instrument in ophtalmology, which replaces, at least in a first evaluation of the patient, the commercial instrument (Retimax CSO). Particularly aimed at the investigation of a signal called pattern reversal visual evoked potential (pr-VEP).Materials and Methods: Epson Moverio BT-200 Smart Glasses are used to generate the pattern reversal stimulus. Electroencephalographic signals, taken through 3 electrodes positioned following the 10/20 international system, is acquired by a commercial acquisition card (OpenBCI Cyton board) and is sent via bluetooth to a PC. Here, through a Matlab algorithm, the data are processed and filtered appropriately in real time, dividing them in epochs of length equal to the time window of stimulus of the reversal pattern and making the average between the epochs obtained.Statistical analysis and Results: After having set up the system introduced a year ago, a recalibration was done on 10 healthy subjects, then a preliminary validation on 11 pathologic subjects, for a total of 42 eyes analyzed. To evaluate its functionalities, the 10 features that characterize the three main waves have been extrapolated from the signal (amplitudes and latencies of N75, P100, N135, amplitudes and relative latencies N75-P100 and N135-P100) and a non-parametric analysis was carried out on them, using various algorithms such as the Kolmogorov-Smirnov test, the scatter plot, the Bland-Altman plot and comparing the averages of the data obtained with the Retimax and the Smart Glasses. Finally, a purely visual evaluation was made, overlapping the signals acquired by the two systems in the same graph. The results show an excellent correlation between the data obtained from healthy subjects and a good correlation between the data obtained from the pathological subjects. The device will soon have to be tested on a large scale to fully analyze the real potential. In the meantime, it will be subject to hardware and software improvements.