Eye Movement
The visual system in the brain is too slow to process information if the images are slipping across the retina at more than a few degrees per second. Thus, for humans to be able to see while moving, the brain must compensate for the motion of the head by turning the eyes. Another complication for vision in frontal-eyed animals is the development of a small area of the retina with a very high visual acuity. This area is called the fovea centralis, and covers about 2 degrees of visual angle in people. To get a clear view of the world, the brain must turn the eyes so that the image of the object of regard falls on the fovea. Eye movements are thus very important for visual perception, and any failure to make them correctly can lead to serious visual disabilities.
Having two eyes is an added complication, because the brain must point both of them accurately enough that the object of regard falls on corresponding points of the two retinas; otherwise, double vision would occur. The movements of different body parts are controlled by striated muscles acting around joints. The movements of the eye are no exception, but they have special advantages not shared by skeletal muscles and joints, and so are considerably different.
Read more about this topic: Human Eye
Famous quotes containing the words eye and/or movement:
“Mine eye and heart are at a mortal war,
How to divide the conquest of thy sight;
Mine eye my heart thy picture’s sight would bar,
My heart mine eye the freedom of that right.”
—William Shakespeare (1564–1616)
“For what we call illusions are often, in truth, a wider vision of past and present realities—a willing movement of a man’s soul with the larger sweep of the world’s forces—a movement towards a more assured end than the chances of a single life.”
—George Eliot [Mary Ann (or Marian)