The idea that osteopathic manipulative treatments (OMTs) should have an impact on the human visual system is not new. Nevertheless, there is a lack of scientific, objective, and experimental evidence. Our goal is to conduct a randomized, double-blind, controlled study to evaluate the effect of OMT on ocular pursuit. Eye movements will be measured by an infra-red video-based eye tracking system with a high spatial and temporal resolution. OMTs will be similar to regular treatments given by osteopaths in their daily practice. We hypothesize that OMT will improve the quality of ocular pursuit.

Our hypothesis is based on the implication of the fascial system (i.e., connective tissues) in the structural continuity that gives form and function to every tissue and organ. Fascial tissue, on which osteopathic manipulations are acting by restoring its elasticity, is also present in the eye cavity. The connection between fascia might explain how osteopathic manipulations, applied on structures which can be far from the original dysfunctional point, might improve oculomotricity.

Before and after OMT, practitioners will estimate the lateral and medial oculomotor muscles' and the fascia's tissue elasticity with a manual test. They will softly mobilize the eyeballs in medial and lateral directions (the amplitude of these passive mobilizations will always be lower than active eye rotations) and give an elasticity score. Before and after these tests, pursuit eye movements will be recorded by an independent technician. Participants will be asked to track a target that will be displaced horizontally on a computer screen. The target will move 30 times from left to right and 30 times from right to left with a constant speed of 20 degrees of visual angle per second.

The study will involve three independent groups (experimental, sham, test-retest) of healthy participants. We expect that pursuit improvement will be larger in the experimental group than in the two other groups. Moreover, as secondary goals, we will evaluate the correlation between pursuit eye movement data (obtained with a technical device, in a standardized situation) and subjective assessments of oculomotor muscles' elasticity made by the practitioners providing OMTs. We will also examine the possible practitioner effect (two exclusive osteopaths will provide OMTs).

Inclusion Criteria:

• Adult between 18 and 35 years of age
• Affiliated to the French Social Security scheme
• Ability to understand and sign the written consent form

Exclusion Criteria:

• Eye movements that cannot be calibrated correctly and therefore measured by the eye-tracker
• Visual deficit that prevents from performing the ocular task
• Pregnancy or breastfeeding
• Neurologic, psychiatric or epileptic disorder, or any other neuromuscular disorder
• Medical treatment affecting the central, autonomous or peripheral nervous system, or affecting vigilance and/or attention
• Skull fracture less than 12 months ago, symptomatic whiplash less than 3 months ago, spinal pain, fever, abdominal or pelvic pain, myopathy, ocular pain, or nystagmus
• Legal protection
• Major risk to develop severe corona virus disease illness, or living with people presenting such a risk

The practitioner providing the actual OMT or sham Treatment will not be involved in collecting eye movement data. The persons collecting eye movement data will not know the group to which participants will have been assigned.