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Misconcept of the Physiology of Eye Movement
CTR 2010-Dec-22 18:58:00
Sorry for posting this somewhat dry scientific information. But since I have done quite a bit of ophthalmology in my active Life Science days, I have to set this straight.
When the eyes scan a picture or a scene o rare reading a line of text, they are moving smoothly around. The movement of the eye can be described in three phases: acceleration - movement - deceleration.
This is wrong..
When the eyes scan a picture or a scene or are reading a line of text, they are jumping from point to point. These jumps are called saccades. The angular velocity of such a saccade depends on their amplitude. While a 10 degree saccade happens with with an angular velocity of 300 degrees per second, a 30 degree saccade will happen with an angular velocity of 500 degrees per second. At a distance of 60 degrees the velocity will reach the maximum speed of 600 degrees per second. When reading normal text (not musical notation or mathematical formulas) the typical duration of a saccade is 20 to 30 milli seconds. These high velocities can only be reached due to the very low inertia of the eye.
So physiologically the eye is jumping at high angular velocities. The phases of acceleration and deceleration are in the range of a few milliseconds.
Viele Gr??e
Carsten T. Rees