Physiology Lab (Phsl 3063, Phsl 3701)

Fall 2012












Lesson Summaries

Review Material


Atlas of Human Cardiac Anatomy


BME Department

Physiology Department

Institute of Technology








EOG Principles

Due to several groups making the same errors, a clarification of the EOG. The EOG does not measure the voltage within the eye. The corneoretinal potential is a constant during the testing you perform in the lab. It can fluctuate within the given range over the course of the day - morning vs. evening, but is not dependent on the direction your eyes are looking.

The deflection on the EOG is due to the relative proximity of the front of the eye to the positive (red) lead. When the eye looks to the right, the front of the eye is closer to the positive lead and there is a positive deflection on the EOG. When the eye looks to the left, the front of the eye is closer to the negative (white) lead and there is a negative deflection on the EOG. The amplitude of the deflection on the EOG is a measure of how far you are looking left or right. If you look 30° to the right you will have an amplitude that is half as high as when you look 60° to the right.

Key Points :
- Voltage of the eye remains constant during the test
- Deflections on EOG are caused by the relative distance between front of the eye and the electrode lead


G at center

OG to the right


Saccades are observed when there is a target-filled environment and your eyes systematically select and fixate on specific targets. Saccades are involuntary movements of the eye. When you read this paragraph, you voluntarily use smooth pursuit motion to move your eyes from left to right across the screen, as you do so, your eyes involuntarily jump between fixation points on each line giving rise to the saccadic staircase pattern as shown in the figure below.

If you are tracking a single target, like a pen or a ball, you do not have saccades. There is only smooth pursuit motion of the eye because there is only one target to fixate upon. Any bumps seen in the smooth pursuit of a single target are due to involuntary flicks, not saccades.

In the horizontal portion shown top right, the eyes move to the left to the beginning of the line (first peak), then there is a consistent upward deflection indicating smooth tracking motion from left to right, the saccades (jumps) are the abrupt increases in height that give the staircase pattern. There is a point at the end of the line of reading where the subject looked to the left to re-read a word as shown by the valley at the end of the trace.

In the vertical portion shown bottom right, the eyes initially moved downward to the beginning of the line (first peak), then remain at a fairly constant deflection level until reaching the end of the line, when the eyes again move downward to the next line of text.

accades during reading








This page was last updated on November 10, 2008