What are the differences between saccades and smooth pursuit eye movements?
Tracking eye movements consist of two different components, namely, smooth pursuit and saccades. Smooth pursuit, or just pursuit, is a class of rather slow eye movements that minimizes retinal target motion. Saccades are rapid eye movements that align the fovea with the target.
What does smooth pursuit test for?
The smooth pursuit test is a test of the central vestibular system, assessing the patient’s ability to accurately track a visual target in a smooth, controlled manner.
What is saccadic movement of eye?
Saccades are rapid, ballistic movements of the eyes that abruptly change the point of fixation. They range in amplitude from the small movements made while reading, for example, to the much larger movements made while gazing around a room.
What causes a saccade?
Saccadic intrusions or oscillations: These saccades occur when patients are fixating in the eye primary position, or they may be superimposed during smooth pursuit. Examples include square wave jerks, macrosaccadic oscillations and ocular flutter/opsoclonus.
What part of the brain controls smooth pursuits?
There are at least two cortical areas that crucially contribute to smooth pursuit and are therefore eligible sites for dynamic gain control: the medial superior temporal area (MST) and the pursuit area of the frontal eye fields (FEFs), which both project to brain stem premotor structures via parallel pathways.
How do you assess saccades?
You should take three parameters into consideration for the analysis of the saccade test: (1) Latency – how long it takes the patient’s eyes to find the target. (2) Accuracy – whether the patient can move his/her eyes to the target without ‘overshooting’ or ‘undershooting’ the target (also referred to as precision).
What is saccadic deficiency?
Ocular Motor Dysfunction – Deficiencies of Saccadic Eye Movements. DEFINITION: A sensorimotor anomaly of the oculomotor system whose characteristic feature is the inability to perform accurate, effective ocular saccadic and/or fixational eye movement patterns.
What part of the brain controls smooth pursuit?
Which part of the brain controls saccades?
The parietal lobe and more particularly its posterior part, the PPC, are involved in the control of saccades and attention.
Is a saccade normal?
In an ideal scenario, saccades are quick and accurate movements. Healthy brains and eyes can normally saccade to a new target in 1/10th of a second or less. However, brain injuries and damaged neural pathways can lead to irregular saccadic eye movements (which we discussed in a past blog).
What is abnormal smooth pursuit?
Smooth pursuit eye movements (SPEM) have also been reported to be abnormal with reduced gain or speed of eye movement and saccadic pursuit (SP). SPEM gain is not easily evaluated clinically and measurement requires laboratory equipment. SP are saccadic eye movements seen during SPEM.
What causes lack of smooth pursuit?
Drugs causing lack of smooth pursuit include depressants, some inhalants, and dissociative anesthetics (such as phencyclidine or ketamine).