What is it?
Saccades are fast eye movements that allow for the voluntary change the direction of gaze quickly. A saccadometer has become the technology of choice for evaluating saccades, because it is non-invasive and objectively analyzes and graphs eye movements moving at several hundred degrees per second (1).
Why is it important?
Saccades are triggered by objects seen or heard, from memory, or as a part of an involuntary natural strategy to scan the environment (1). It is important to study saccades because of the many areas of the brain it takes to generate not only fast, but, appropriate, purposeful, and accurate movements. Saccades are analyzed using three different characteristics including, latency, amplitude, and velocity. Studying these is a way to gain insight into the function of specific parts of the brain and neural pathways.
How does it work?
From the initial presentation of a stimulus, it takes approximately 200 milliseconds for the inhiation of an eye movement to occur, during which time, neural processing amongst the retina, cerebral cortex (frontal lobe), superior colliculus, cerebellum and vestibular system is occurring (1,3). This latency, or time it takes to process the target presentation, is used to understand aspects of saccade programming associated with visual processing, target selection, and motor programming (1-3), strongly associated with the integrity of the frontal lobe (executive center) and superior colliculus. To achieve clear, stable, single vision, the control of eye movements must be accurate, relying heavily on the vestibular system (balance and coordination center) and cerebellum (fine motor movement center), to reference spatial maps in order to generate appropriate velocity and position commands (1). Because saccades are brief, vision cannot be relied on to guide the eye to the target (4), therefore, the speed, or degrees per second (velocity), in which the eyes move to the intended target becomes important so that no disorientation occurs during this time.
How does it help?
One of the most impressive aspects of ocular motor control is the way in which the brain constantly monitors its performance, and in the face of disease and aging, adjusts its strategies accordingly (5). Therefore, the evaluation of saccades, due to the immense coordination and integration needed, is a valuable tool to identify different disorders that can have pathognomonic abnormality shifts (5). For example, diseases targeting the cerebellum, may have subclinical findings that may be identified in areas affecting associations with spatial orientation, memory, cognition, or motor control (1). Other conditions affecting these aforementioned association areas that may have an effect on saccadic function are, but not limited to, Multiple sclerosis (6), Parkinson’s Disease (7,8) and/or stroke (9), neurodevelopmental disorders, degenerative diseases, etc.