Saccadometry is an ocular motor test that allows for the functional evaluation of the varied brain regions and circuits involved in the generation of fast, appropriate, purposeful, and accurate saccadic eye movements. Saccades are traditionally analyzed using three different characteristics including latency (the time between stimulus presentation and eye movement initiation), amplitude (the height of the trajectory), and velocity (the rate at which the eye moves across the visual field). Saccadometry adds the analysis of phase data, which provides further insight for lesion localization. The antisaccadic system can be explored using antisaccade testing, which offers windows into cognition and executive function.
In the early 2000s, the saccadic system was already known to be associated with executive function. However, we did not yet have the technology to test how different subfunctions of the brain were related to performing tasks such as antisaccade testing. This deeper dive into sacaddic testing can provide clinically actionable insights into neurological disorders such as concussion and traumatic brain injury, neurodegenerative diseases (e.g., Alzheimer's disease), movement disorders (e.g., Parkinson's disease), depression, attention-deficit disorders, among many others.
The ability to suppress reflexive responses in favor of voluntary motor acts is crucial for everyday life. The antisaccade test can assess both abilities; to suppress and to make the voluntary jump. This task requires subjects to suppress a reflexive prosaccade (a tendency to look at something that one is not supposed to look at) and instead to generate a voluntary saccade (a specific type of eye movement) to the opposite side. Current data show that a variety of brain lesions, neurological diseases and psychiatric disorders result in errors, i.e., prosaccades toward the stimulus, in this task. Brain imaging studies have shown that a widely distributed cortical and subcortical network is active during the generation of antisaccades.
The response inhibition demonstrated in antisaccade testing has been demonstrated in ADHD. The dorsolateral prefrontal cortex has also been demonstrated to be a critical region for the regulation of affect. Impaired antisaccade performance has been studied as a sensitive biomarker for psychological conditions ranging from chronic depression to schizophrenia. Relationships of prosaccades and antisaccades can also provide insight into executive function disorders ranging from Mild Cognitive Impairment to Alzheimer’s disease and Frontotemporal Dementia.
With our new advancements in technology, we can use these tests in quantifiable ways to find out about mental conditions and disorders. The tests help us connect these different functions and become better equipped towards properly diagnosing them and understanding what is going on in their brains and minds.
The Interacoustics VisualEyes 505 provides an ideal environment for fixation-free observation and recording of eye movements, including antisaccade testing. Included is the Video Frenzel system, which incorporates a detection algorithm, and provides an efficient way to diagnose patients who have potential vestibular disorders. Interested in adding this powerful system to your practice? Contact e3 Diagnostics for a quote today!
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