Eye-catching: Our eyes are in constant motion

If our optic nerve were to transmit all of the signals it receives in the retina at the resolution to which we are accustomed to, it would have to be the diameter of an elephant’s trunk. Only a minuscule area of the retina known as the fovea is able to provide fine detail resolution. In order to give everything that we see a chance to pass through the fovea, we must move our eyes around rapidly and frequently. These eye movements are called saccades.

“Visual masking” is one of the reasons why saccades don’t cause our view to be one massive blur of motion. It occurs when objects that are in clear sight when our eyes don’t move make a more vivid impression than the blur when our eyes are moving. Scientists believe that the human brain suppresses the signals that reach our retina while saccades are occurring. In addition, our brain remaps what we are seeing before we move our eyes to switch from one view to the one that shows up after the saccade. Cells in the brain know that a saccade is on the way from another signal in the brain that gives the command for eye movement. This coordinates what we see and where we will look next. The fusion of these images during saccades helps us to understand that things we saw before and after a saccade are actually the same even if they have moved or the light has changed.

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