Saccade Analytics utilizes virtual reality (VR) eye-tracking technology to record data from 6 cameras per eye and extremely sensitive gyroscopes. This revolutionary technology is a game changer for patients with a previous concussion or vestibular dysfunction, as it provides an objective measurement of brain function.
One of the biggest challenges with concussion management is that it is a functional, not a structural injury. Meaning there is no advanced imaging (MRI, CT) or blood test currently available to determine if a patient has sustained a concussion. The other difficulty with concussion management is that because it is a functional injury, healthcare providers must rely on symptoms (subjective data) to determine if a patient is recovering. This is also true for patients with vestibular hypofunction as the majority of test rely on subjective data.
Saccade Analytics also allows patients to track their progress over time. This is very important as the majority of concussion tests (i.e. SCAT) are only valid for a couple days following an injury.
Saccade Analytics is the product of over 60 years of research on eye and head movement. It was developed by Dr. Mimi Galiana, a professor and researcher from McGill University who is a leading expert in the field of vestibular ocular dysfunction with over 200 publications.
What does Saccade Analytics Test?
Saccade Analytics is a 10 minute test that utilizes VR eye-tracking technology to objectively measure a patient’s eyes and head while they perform 8 simple tasks. Each task is designed to test a specific brain function.
Smooth Pursuits (Head-Fixed and Head-Free):
Smooth pursuit eye movements are important for maintaining fixation on a target as it moves randomly across a patient’s field of view. An example of this is following a ball with your eyes and catching it, or reading words on a page.
Smooth pursuit testing is usually only done in the head fixed-position with a constant pattern (horizontal or vertical). The advantage of Saccade Analytics is that it can test smooth pursuits with the head-free and fixed. Head-free smooth pursuits’ incorporates movement from the neck. The test utilizes a randomized pattern to provide a functional representation of real-life movement (i.e. soccer goalie following a ball). Head-fixed smooth pursuits’ isolates the muscles that control eye movement (oculomotor).
Saccade Analytics records the angle between the eyes (vergence) while performing the task, accuracy of the eyes to follow a target and the number of corrective eye-movements (saccades). A high number of corrective eye-movements (saccades) during smooth pursuits indicate poor speed perception. For example, patients with eye-movements slower than the speed of a target will have catch-up saccades making the target appear faster. Whereas, patients with eye-movements faster than the speed of a target will have backwards saccades making the target appear slower. Saccades are a common clinical finding seen in concussion patients.
Testing smooth pursuits provides objective data on the functional ability of large areas of the brain; such as: middle temporal area, vestibular nuclei, dorsolateral pontine nuclei, frontal eye field and the visual cortex.
Active Visual Vestibular Ocular Reflex
The Vestibular Ocular Reflex (VOR) is responsible for the coordination of head and eye movements. During brief, rapid movement of the head, the vestibular system sends nerve signals to the muscles that control the eyes to cancel out the head motion. For example, if a patient looks straight forward while moving their head quickly to the left. The vestibular system in the left inner ear will detect the motion and send nerve signals to the eyes to move them the same distance and speed to the right. An example of this is when a person is walking or running. The VOR allows the eyes to cancel out the movement of the head. Without this reflex, it would appear as though a person was looking through a camera (shaky lens vision) every time they went for a walk or run.
Saccade Analytics records the angle between the eyes (vergence) while performing the task, VOR gain and VOR slip velocity. VOR gain is the eye velocity relative to the head velocity. VOR slip velocity is the speed (degrees per second) at which the eyes are no longer able cancel out the motion of the head.
Patients with a dysfunctional VOR often report blurred vision, unsteadiness, nausea and dizziness. Concussion patients often report dizziness (30-60%) as a symptom on their initial visit. Vestibular dysfunction has also been shown to impact cognitive function; such as: attention and memory. Decreased attention and poor memory are also common persistent post-concussion symptoms.
A Saccade allows the eyes to work in unison to shift their gaze from one target to another. An example of this is a defender looking from one attacker to another.
Saccade Analytics records the angle between the eyes (vergence) while performing the task, accuracy of the eyes to lock onto a new target (over or undershoot) and the reaction time.
Studies have shown that a delayed saccade reaction time may be indicative of diseases of higher brain functions; such as: ADD, Parkinson and concussions
Antisaccade testing measure the ability of an individual to inhibit a reflex while mapping their peripheral vision.
The test requires a patient to look straight forward while a distracting target is presented in their peripheral vision. Patients have to inhibit the reaction to reflexively look at a target and are instructed to guess the distance of the target from a center point in the opposite direction. For example, a target is presented 3 cm to the right from a center position and patients have guess where 3 cm to the left would be.
Saccade Analytics records the angle between the eyes (vergence) while performing the task, accuracy of the individual to estimate the correct distance in the opposite direction, the reaction time and the ability to inhibit the reaction of reflexively looking at a distraction target.
Antisaccade testing evaluates the function of the visual cortex and poor results have been found in concussion patients. Research has also shown Antisaccade testing to be an accurate side-line concussion assessment that is also valid over an extended period of time.
Optokinetic nystagmus (OKN) is reflex that occurs when someone is exposed to a repetitive visual stimulus. An example of the optokinetic reflex (OKR) is a person looking out the window of a speeding car with numerous road signs going past. The OKR involves 2 types of eye movements. The first eye movement is a slow, smooth pursuit where the eyes follow a target. The second type is a rapid eye corrective movement (saccade) to re-fixate the eyes on another target. Going back to our example, the slow smooth pursuit movement would be the eyes following a road sign as it leaves a person’s field of view. The rapid saccadic re-fixation would be the eyes locking onto a new road sign.
Saccade Analytics records the angle between the eyes (vergence) while performing the task, OKN gain and OKN slip velocity. OKN gain is the eye velocity relative to the target velocity. OKN slip velocity is the speed (degrees per second) at which the eyes are no longer able to re-fixate onto a new target.
Optokinetic nystagmus testing evaluates large parts of the brain; such as: prefrontal cortex and occipitotemporal cortex. Dysfunctions of the OKR are present in patients with vestibular complaints and previous concussions. Furthermore, patients with a previous concussion often report increased symptoms while in a busy visual environment. An example of a busy visual environment is being in a grocery store or driving.
Spontaneous & Gaze-Evoked Nystagmus
Spontaneous nystagmus is the involuntary, rapid eye movement that occurs when there is no visual, vestibular or cognitive stimulus. The purpose of testing for spontaneous nystagmus is to determine if there is an underlying neurological issue.
The test requires a patient to maintain their gaze fixated on a target (white dot on a black back ground). The target disappears and the patient has to maintain their gaze where the dot used to be. A new target will appear and the patient has to look at the new target.
Saccade Analytics records the mean number of corrective eye-movements (saccades) per second during fixation (tremor frequency), average drift of the eyes (difference between the starting and end position while no target is present) and the average eye velocity during the fast phase of the corrective eye-movement (saccade).
There are many causes of nystagmus; however, the most common form of nystagmus occurs with eccentric gaze. This form of nystagmus occurs when the eyes are forced to look up and to the side, and may indicate a cerebellar or brainstem disorder. Patients who present with vertigo will have a horizontal nystagmus that is suppressed when they look at a target (fixation). It is important to test spontaneous nystagmus in patients with a previous concussion to rule out any more serious injuries.