EOG provides to sens of corneo-retinal potential which occurs between front and back side of human eye. Resulting record of EOG is called as electrooculogram.Applications of EOG are; ophthalmological diagnosis, recording of eye movements.
Cornea has a positive charge and retina has a negative charge influenced by depolarization of basal membrane (RPE) caused by photostimulation.Thus, eye is a dipole. EOG is measured near the eyes using the electrodes which are placed on the skin.Electrodes can be stickers or cup electrodes which are using by electroconductive gel.
Amplitude of EOG varies between ~100 µV to ~1 mV. Changes in amplitude are aprox. 5 – 20 μV to 1° of view angle. Detection of small angles (1-2°) is difficult.Most energy of EOG lays in band up to 30 Hz.
Measured potential is proportional to eye bulb rotation and to intensity of environment illumination.
There are different eye movement forces for different people. EOGanalyze different eye movement levels that will cause different control signals. The eye movement signals obtained from the horizontal position of electrodes will represent the right and the left directions.The eye movement signals obtained from the vertical position of the electrodes will represent the up and down directions.We can observe it with graphics.
Right-Left Movement
Up-Down Movement
If we are examining the horizontal movement, there will be a sudden rise in the graph at the time of the blink.If we are examining vertical movement, there will be a sudden decrease in the graph at the time of blinking.
The status of the RPE layer and the name and level of the diseases caused by this may be possible by considering clinical findings. In diffuse diseases of the retinal pigment epithelium, the electrooculography response is significantly affected. In the autosomal dominant Best disease and carriers, the results of coronary electrooculography are normal. Sometimes people with low vision may not be able to understand the cause by standard examinations and examinations. In these cases, EOG is guiding.
