We are excited to share insights into the potential of eye tracking. Every month, we keep you updated on the latest news shared by the scientific community.
The current newsletter will emphasize the latest research about Multiple Sclerosis (MS) and the view of clinical experts on the relevance of eye-tracking for MS.
Enjoy the reading!
The neuroClues® Team
New research is focusing on non-invasive techniques, including oculomics, which studies ocular manifestations related to systemic diseases. This includes analyzing changes in the retina and optic nerve, which are directly linked to brain health, as well as novel biomarkers in ocular fluids and eye-tracking movements.
There are two common saccadic disorders observed in patients with MS:
I. Ophtalmoparésie Internucléaire (INO)
INO occurs due to the demyelination of nerve fibers in a specific brain region called the medial longitudinal fasciculus (MLF) located in the pons. When the signals are disrupted, it leads to a condition where the eye that is supposed to move inward (adducting eye) does so more slowly than the eye moving outward (abducting eye) during horizontal saccades. This miscoordination is termed as adduction lag.
Indeed, INO can be clinically observed as dissociated nystagmus in the abducting eye. However, incorporating eye tracking into consultations can detect INO at earlier stages, even when it is not visible to the naked eye. Eye tracking also provides objective measurements of INO and tracks its progression over time with different treatments.
II. Saccadic Dysmetria
It is caused by lesions in the cerebellar peduncles. These lesions impair the smooth pursuit movements and the ability to suppress the horizontal vestibulo-ocular reflex (VOR), which is essential during tasks that require tracking moving objects with combined eye-head movements.
Saccadic dysmetria can present as gaze-evoked nystagmus (GEN) or downbeat nystagmus (DBN), each linked to specific neural deficits. GEN results from a defect in the neural integrator network, while DBN is due to loss of inhibitory control by the cerebellum on the vertical semicircular canals.
This paper highlights the potential of eye-tracking technology as a non-invasive tool for objectively quantifying saccadic disorders, which can assist in early diagnosis, monitoring disease progression, and evaluating treatment response in MS patients.
The double-step saccadic test requires executing two rapid saccades towards sequential stimuli, engaging multiple cortical and subcortical networks. This complexity makes it a more sensitive indicator of cognitive and motor function than simpler tasks like single-step saccades. It can detect subtle changes in eye movement control, offering a nuanced view of disease progression or treatment response in multiple sclerosis.
The study demonstrates that the double-step saccadic test has stronger statistical correlations with clinical, cognitive, and MRI metrics compared to traditional saccadic tests. For instance, individuals with multiple sclerosis showed a significantly lower proportion of correct double-step saccades compared to healthy controls, with these results correlating with grey matter atrophy, lesion load, and cognitive impairments.
Proposed as a novel outcome measure for remyelination trials, the double-step saccadic test offers a promising alternative for assessing treatment efficacy by reflecting both structural damage and cognitive function, addressing a key limitation of many traditional eye movement assessments.
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