This study aims to develop and validate a sensitive and non-invasive eye-tracking software application.

This study will obtain participant responses to brief cognitive tests designed to evaluate several key functions known to be affected by MS and non-invasive eye movement measurements in response to visually presented stimuli during specifically designed eye-tracking tests. The study data will be used to develop machine learning algorithms and validate a software application intended to track the progressive component of multiple sclerosis and associated cognitive changes.

Inclusion Criteria:

• Able to provide informed consent.
• Aged 18 years or older at the time of enrollment.
• Able to read in either French or English.
• Visual acuity of 20/100 in at least one eye (corrective glasses, contact lenses, surgery etc.

are permitted)

For patients only:

• Confirmed diagnosis of MS with no signs of progressive increase in physical disability within the past six months.
• Neurological condition is medically stable during the study visit.
• Expanded Disability Status Scale (EDSS) score 0 - 8.0 at the initial visit.

Exclusion Criteria:

• Evidence or medical history of psychiatric issues that are known to also affect movements and oculomotor control.
• Presence of co-morbid neurological conditions to avoid eye movement anomaly confounds (Strabismus, cranial nerve palsy, stroke-causing hemianopsia).
• Diagnosis of macular edema or other pre-existing ocular conditions that would prevent a participant from performing the eye movement assessments.
• Recent (less than three months from enrollment) start of, change of dose, or irregular use of, new prescription drugs known to influence ocular motor visual function, such as benzodiazepines, antipsychotics and anticonvulsants. Occasional use of benzodiazepines for medical procedures is permitted, at the investigator's discretion, but should not occur within a short time period prior to or during an eye movement assessment.

For healthy controls only:

• Evidence or history of significant neurodegenerative disorder affecting brain function, e.g., multiple sclerosis (MS), Parkinson's disease (PD), Amyotrophic lateral sclerosis (ALS), Dementia.

For MS patients only

• Diagnosis of Clinically Isolated Syndrome (CIS), Radiologically Isolated Syndrome (RIS) or Primary Progressive MS (PPMS).
• Patients who are currently experiencing a relapse or who have experienced a relapse within the last three months. A relapse is defined as appearance of a new neurological abnormality or worsening of previously stable or improving pre-existing neurological abnormality, separated by at least 30 days from onset of a preceding clinical demyelinating event (McDonald et al. 2001). The abnormality must have been present for at least 24 hours and occurred in the absence of fever (< 37.5°C) or known infection.
• Patients who have been undergoing disease-modifying therapy for less than three months

The target sample size for the MS group is 120. Eligible patients will be stratified based on their EDSS score. Based on the known distribution of EDSS scores, we will recruit 46 MS patients with a score between 0-2, 46 patients with a score between 2.5-4, 23 patients with a score between 4.5-6.0, and 23 patients with a score between 6.5-8. Data will also be acquired from a control group (n=30) that will be frequency-matched for age.