WEEK ONE

Bismillahirrahmanirrahim.

As the first week of s1’13 starts, I was assigned to build a project for my final year project. The first things-to-do are to find supervisor for my project. He, which I choose Sir Syazwan Md Yid will be advising me on and about the project. In this week also, there is the first briefing for all final year students for bachelor program and engineering design for diploma students.

This project is mainly about the electrooculography or EOG. EOG is a biomedical technique for measuring the resting potential of the retina while the electrooculogram is the resulting signals of the potential difference caused by the eye movements. This technique use recording the eye movements non-invasively using skin surface electrodes placed around the eyes. The main applications are in ophthalmological diagnosis and in recording eye movements. EOG interfaces also let users who can’t manipulate a mouse or track pad with their hands move a cursor on a computer screen.

The voltage difference is measured between the cornea and the retina. The resting potential ranges from 0.4mV to 1mV and a pair of electrodes are commonly used to detect this signal. Depending on the eyes' position, an electrode is more positive or negative with respect to the ground electrode. Therefore, the recorded signal is either negative or positive when moving the eyes.

This can be monitored using bipolar electrodes in two basic configurations which are two channel configuration and four channel configuration. The two channel configuration is designed to detect movement onset and direction in a single plane which is horizontal while four channels configuration is designed to detect movement onset and direction in any plane which is horizontal and vertical. However, the voltage differences when there is an eye movement can be just small microvolts. So, the EOG system must amplify the voltage in order to get a readable signal for the oscilloscope or CPU. This is because the oscilloscope and CPU cannot detect the small voltages from the EOG system. 

TWO CHANNEL ELECTRODE CONFIGURATION

I will explain more about EOG system in the next post :)

Barakallah.