Evaluation of Efficacy and Safety of Vismed Gel Multi 0.3% Versus Vismed Multi 0.18% on Treatment of Ocular Dryness

Inclusion Criteria: * Sex: male or female. * Age: more than 18 years. * Subject with a moderate to severe dry eye syndrome needing artificial tears in the 3 months preceding the inclusion. * Subject having used only artificial tears without preservative (NaCl 0.9%, Hydrabak®) during 1 to 2 weeks before inclusion (up to 6 times a day). * Subject with a score ≥ 6 for the 5-Item Dry Eye Questionnaire (DEQ-5) * Subject with at least one eye with: * Global ocular staining (cornea and conjunctiva) ≥4 and ≤9 on the Oxford scale (0 to 15) AND one of the following criteria: * Schirmer test ≥ 3 mm/5 min and ≤ 9 mm/5 min OR * Sum of 3 measurements of Tear film Break-Up Time (TBUT) ≤ 30s. * Subject, having given freely and expressly his/her informed consent. * Subject who is able to comply with the study requirements, as defined in the present CIP, at the Investigator's appreciation. * In France: subject being affiliated to a health social security system. Female subjects of childbearing potential should use a medically accepted contraceptive regimen since at least 12 weeks before the beginning of the study, during all the study and at least 1 month after the study end. Exclusion Criteria: * Pregnant or nursing woman or planning a pregnancy during the study. * Subject deprived of freedom by administrative or legal decision. * Subject in a social or health institution * Subject who is under guardianship or who is not able to express his/her consent. * Subject being in an exclusion period for a previous study. * Subject suspected to be non-compliant according to the Investigator's judgment. * Subject wearing contact lenses during the study. * Far best corrected visual acuity \< 1/10 * Subject with severe ocular dryness with one of these conditions: * Eyelid or blinking malfunction * Corneal disorders not related to dry eye syndrome * Ocular metaplasia * Filamentous keratitis * Corneal neovascularization * Subject with severe meibomian gland dysfunction (MGD) * History of ocular trauma, infection or inflammation, not related to dry eye syndrome within the last 3 months prior to the inclusion. * History of ocular allergy or ocular herpes within the last 12 months. * Subjects who underwent ocular surgery, including laser surgery, in either eye within the last 6 months. * Any troubles of the ocular surface not related to dry eye syndrome. * Subject having used artificial tears in the 6 hours preceding the inclusion visit. * Use of the following ocular treatments: isotretinoïd, cyclosporine, tacrolimus, sirolimus, pimecrolimus, punctual plugs during the month preceding the inclusion. * Subjects who have received ocular therapy (either eye) with any ophthalmic medication, except tear substitutes, within 2 weeks prior to study start or expected to receive ocular therapy during the study. * Any not stabilised systemic treatment, which can have an effect on performance or safety criteria, at the investigator appreciation.