ELECTROOCULOGRAPHY

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Presented by-

SHAKIL MUHAMMAD

UET PESHAWAR

PAKISTAN

INTRODUCTION

Eyes are our window to this large universe.

Advancements in the field of biomedical electronics and in the

field of electronics and communication system have changed the

perception of eye.

It is estimated 150,000 severely disabled persons able to control

only the muscles of their eyes without any problem.

ELECTROOCULOGRAPHY

Electrooculography (EOG) is a technique

for measuring the corneo-retinal standing

potential that exist between the front and the

back of the human eye. The resulting signal

is called the ELECTROOCULOGRAM.

Four to five electrodes, 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.

ANATOMY OF THE EYE

THE ELECTROOCULOGRAM

The human eye is an electrical

dipole with positive pole at cornea

and negative pole at the back of eye

(retina).

This difference is due to the large

presence of electrically active nerves

in the retina compared to the front of

the eye.

The magnitude of this corneoretinal

potential is in the range 0.4-1.0 mV.

EOG Detection

Four to five electrodes are reqd.

The electrodes act as transducers.

Two electrodes are placed on the outer side of the eye.

Another pair above and below the eye

And a reference electrode

…contdPlacement of electrodes

Horizontal

Vertical

Reference

EOG Signals

HEOG Signals: Obtained from horizontal eye movements

Eye movement: from centre to left: +ve voltage spike

from center to right:-ve voltage spike

VEOG Signals: Obtained from vertical eye movements

Eye movement: from centre to top: +ve voltage spike

from centre to bottom: -ve voltage spike

Blink Signals: Obtained due to blinking of eyes

Voluntary Blink Signals

Involuntary Blink Signals

EYE MODEL BASED IN EOG

FUNCTION OF EACH BLOCK:

FILTER eliminates the effects due to other biopotentials and are

passed through high and low frequencies.

SECURITY BLOCK detects when the eyes are closed and in this

case, the output is disabled.

If a SACCADIC MOVEMENT is detected, a POSITION

CONTROL is used, whereas if a SMOOTH MOVEMENT is

detected, a SPEED CONTROL is used to calculate the eye

position.

The FINAL POSITION (ANGLE) is calculated as the sum of the

saccadic and smooth movements.

EOG Signal Filtering and

Acquisition System

APPLICATIONS

Electrooculographic Guidance Of A

Wheelchair Using Eye Movements

Eye Movement Controlled

Human-Computer Interface

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 laptop (or a microprocessor)

A ZigBee wireless module

….contd

ADVANTAGES

The EOG is easy to use.

The signals are measured with respect to the eye muscles.

Registration of eye movements with closed eyelids and during sleep are

possible.

The EOG is the most inexpensive eye movement recording system.

CONCLUSION

This technique has resulted in rapid advancements in the design of human

computer interfaces for severely paralyzed patients, with the aid of this

technology many disabled patients who are unable to speak or move their

limbs can access many electronic devices such as fan, light etc only through

the movement of their eyes.