Brief Introduction on Electro Oculography-SSM.pptx

Brief Introduction on Electro Oculography

1. ELECTRO OCULOGRAPHY MUKESH SUNDARARAJAN

2. It is a technique for measuring the resting and action potential of the retina. Five electrodes, and the amplifiers and filters are required Usually, pairs of electrodes are placed either above and below the eye or to the left and right of the eye.

3. PRINCIPLE The eye acts as a dipole in which the anterior pole is positive and the posterior pole is negative. Left gaze: The Cornea approaches the electrode near the outer Canthus of the left eye, resulting in a negative-trending change in the recorded potential difference. Right gaze: the Cornea approaches the electrode near the inner Canthus of the left eye, resulting in a positive - trending change in the recorded potential difference.

4. The EOG is the electrical signal produced by the potential difference between the retina and the cornea of the eye. This difference is due to the large presence of electrically active nerves in the retina compared to the front of the eye. Eye movement will respectively generates voltage up to 16µV and 14µV per 1° in horizontal and vertical way.

5. EYE MOVEMENTS  anterior pole

6. EOG Detection

7. Placement of electrodes Horizontal Vertical Reference

8. EOG Signals HEOG Signals: Obtained from horizontal eye movements Eye movement: from center to left: + ve voltage spike from center to right:- ve voltage spike VEOG Signals: Obtained from vertical eye movements Eye movement: from center to top: + ve voltage spike from center to bottom: - ve voltage spike Blink Signals: Obtained due to blinking of eyes Voluntary Blink Signals Involuntary Blink Signals

9. Block diagram

10. GRAPH

11. ELECTRODES : Ag-AgCl Electrode: It is a type of reference electrode. The electrode is a silver wire that is coated with a thin layer of silver chloride. They are inexpensive to manufacture, are simple construction and have stable potential. Metal disk electrode: They are generally made of high purity tin, silver, gold or even surgical steel Application area is near the eye region Diameter range is 4-10mm

12. APPLICATIONS Electrooculographic guidance of a wheelchair using eye movements. A portable wireless eye movement-controlled Human-Computer Interface for the Disabled.

13. Human Computer Interface(HCI) is a device used by the disabled who have motor paralysis and have difficulty in conveying their intentions. The only muscle they can control are the eye muscles. It is a real time communication system based on EOG signal It has four major parts Five electrodes A two channel amplifier A microprocessor A wireless module

14. ADVANTAGES Range Linearity Obstacles in front of the eye Cost Eye closure is permissible Real Time

15. DISADVANTAGES One potential problem, depending upon the nature of the experiment would be for the subject to change the gaze by turning the head. The potential difference between the retina and the cornea may vary with such factors as light adaptation, diurnal variations and the degree of alertness.

16. THANK YOU