HELIX, a Double-masked Study of SYL1001 in Patients With Moderate to Severe Dry Eye Disease (DED)

Inclusion Criteria: * Both genders * ≥ 18 years old * Give written informed consent to participate in the study after having been informed of the study design, objectives and possible derived risks * Common symptoms of persistent, daily, moderate to severe dry eye lasting more than six months. * Use of artificial tears * VAS scale for eye discomfort/pain between 30 - 80 * CFS ≥ 2 and ≤ 4 on the Oxford scale * TBUT \< 10 seconds * Hyperemia score ≥ 1 (McMonnies scale) * Schirmer's test without anesthesia ≥ 2 and \< 10 mm/5min in the eye * Corrected visual acuity ≥ 0.7 logMAR Exclusion Criteria: * Pregnant or breastfeeding females or those with a positive pregnancy test. * Females of childbearing potential who will not use a medically acceptable contraceptive method from selection and during the whole study. * Current relevant disease, including respiratory disease, cardiovascular, endocrine, neurological, haematological, renal, neoplasic, hepatopathy, gastrointestinal distress, hypertension, or infectious acute processes. * Past history of a chronic o recurring condition that could interfere with study according to the investigator's judgement. * Concomitant use of other drugs with analgesic activity by any route of administration at the enrolment period. * Changes in any ocular and/or systemic concomitant medication one month prior to the study commencement and during the study development. * Changes on the preestablished artificial tears dosage 15 days prior to the study commencement and during the study development. * Cyclosporine treatment initiation or changes in cyclosporine dosage or dosing regimen during the 6 months prior to enrolment. * Previous history of drug hypersensitivity. * Use of contact lenses * Case history of drug or alcohol abuse or dependence. * Relevant abnormal laboratory results as judged by the investigator * Previous refractive surgery * Participation in a clinical trial within 2 months before the enrolment visit * Relevant ocular pathology judged by the investigator.