Clinical Investigation Between the Topical Administration of a Tear Substitute With Ancillary Medicinal Substance and Hyaluronic Acid 0.3% (FBV_01) vs Hyaluronic Acid 0.3% in Subjects in the Treatment From Moderate to Severe DED

Inclusion Criteria: * Patients able to provide written Informed Consent, in accordance with good clinical practice and current legislation; * Patients (male and female) 18 years of age or older with moderate to severe dry eye syndrome or with dry eye syndrome, even after eye surgery (e.g. refractive surgery or cataract); * Moderate to severe dry eye syndrome in one or both eyes in the presence of: 1. Dry Eye Symptom Assessment Questionnaire (SANDE) \> 60; 2. Tear Film Break-Up Time (TFBUT) \< 7 seconds. TFBUT value will be recorded as an average of 3 measurements; 3. Test di Schirmer \< 10 mm; * Diagnosis of dry eye syndrome for at least 6 months (use or recommendation of use of artificial tears/lubricants for the treatment of dry eye); * Patients able to understand the nature and purpose of the study, including possible risks; * Patient able to cooperate with the Investigator and meet the requirements of the clinical investigation plan; * Patient who, in the opinion of the Investigator, will benefit from this treatment; * Patient available for the entire study period. Exclusion Criteria: * Eye infection or clinically significant inflammation in both eyes (for example: Herpes simplex infections, corneal virus infections, bacterial, viral or fungal conjunctivitis, tuberculosis and mycosis of the eye, purulent and herpetic blepharitis, stye); * History or evidence of eyelid abnormalities in either eye; * Use of topical cyclosporine, topical corticosteroids, or any other topical medication for the treatment of ocular pathologies in either eye within 7 days of study enrollment; * Patients being treated with chronic systemic therapies with analgesic, anti-inflammatory, corticosteroids, or opioids; * History of ocular surgery (including laser procedures or refractive surgery) in either eye 7 days prior to enrollment; * History or evidence of severe or uncontrolled systemic or autoimmune disease does not allow participation in the study or could impair the results; * Patients being treated with drugs and/or medical devices and/or supplements for neuropathic pain (e.g., SNRIs (duloxetine, venlafaxine), pregabalin, gabapentin, TCAs (nortriptyline, amitriptyline)); * Patient with known or potential allergy or hypersensitivity and/or history of allergic reactions to one of the components of the medical device; * Participation in another clinical trial within 30 days prior to the screening visit; * History of administration or abuse of drugs, medications, or alcohol; * Women of childbearing potential (those who are not surgically sterilized or post-menopausal for at least 1 year) will be excluded from participation in the study if they meet any of the following conditions: 1. are currently pregnant or, 2. have a positive urine pregnancy test result at visit 1, 3. intend to become pregnant during the study treatment period or, 4. are breastfeeding or, unwilling to resort to highly effective birth control measures, such as: hormonal contraceptives oral, implanted, transdermal or injected and/or mechanical barrier methods spermicidal concurrently with a barrier such as a condom or diaphragm or IUD during the entire course of the study and 30 days after the end of the treatment period; * Subject unable to follow clinical investigation procedures and follow-up visits; * Any other medical condition which, in the opinion of the Investigator, could influence participation in the clinical investigation or compromise its results.