Saccades are rapid eye movements that allow us to focus on small areas of our surroundings. There are four types of saccadic movements, and they can be used to detect neurological problems. Saccades are controlled by the frontal and median eye fields in the brain, and visual saccadic suppression blocks blurry images from reaching the brain. Disorders that affect saccadic eye movement include nystagmus, under-and-over dysmetry, and glissade.
A saccade is an eye movement when both eyes move rapidly in tandem. This could be accompanied by movement of the head, neck or other parts of the body. It is a process of the brain that allows the viewer to perceive the world around them in small focused areas. The speed and path of a saccade can be used to detect some neurological problems.
There are four distinct types of saccadic movements. Visually guided saccades show the eye moving towards a newly introduced image. Memory-driven saccades will show the eye moving to a place that is remembered but not necessarily present. Predictive saccades are when the eyes predict the movements of an object in the visual field and follow it. Finally, anti-saccades are when the eye moves away from an object sometimes expecting a movement that doesn’t occur.
Several methods and machines can be used to test whether saccades in a human are working as they should. These tests measure the speed of eye movement both vertically and horizontally. Some conditions can be diagnosed if the speed is too fast or too slow in either direction, including excessive throbbing and dysmetria.
Saccadic movement is primarily controlled by the frontal eye fields, which are areas of the brain located near the top of the head. A second area known as the median eye fields helps control the eye’s physical tracking movements, especially during a saccade. When combined, the eyes are capable of rapidly moving and fixating on areas of the surrounding environment allowing a detailed, three-dimensional mental image of the area to be established.
The human eye is the fastest moving part of the body during a saccade and has therefore developed a mechanism known as visual saccadic suppression. This eye function will block an image that the eye perceives as blurry from reaching the brain. This avoids transmitting meaningless information to the brain when it would be impossible to process it.
There are several disorders that can affect saccadic eye movement in humans. One of the most common is known as nystagmus and is characterized by slow tracking followed by fast saccades afterward. Under-and-over dysmetry is a disorder in which the eyes overcompensate or undercompensate when trying to fixate on one point. A glissade is a type of saccadic jam in which the eye does not stop at a fixed point but slowly moves past the point.
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