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

The goal of this clinical investigation plan is to evaluate the performance, tolerability, safety, and compliance of an ophthalmic solution containing an ancillary medicinal substance and hyaluronic acid 0.3% (FBV\_01) compared with hyaluronic acid 0.3% alone in adult men and women (≥18 years) with moderate-to-severe dry eye syndrome. The main questions it aims to answer are: * Is the ophthalmic solution containing an ancillary medicinal substance and hyaluronic acid non-inferior in improving the clinical performance outcomes of dry eye compared with hyaluronic acid alone? * Is the investigational device safe and well tolerated, with acceptable partecipant compliance over the treatment period? Researchers will compare the medical device containing an ancillary medicinal substance and hyaluronic acid 0.3% (FBV\_01) to hyaluronic acid 0.3% alone to see if the combination provides at least equivalent clinical benefit without increased safety issues. Participants will be randomly assigned (1:1) to one of two treatment groups in a multicenter, prospective, randomized, open-label, controlled study. Participants will instill 1 drop in both eyes 4 times daily (every 4 ± 1 hours) for 30 ± 4 days and attend study visits for assessments of dry eye signs and symptoms, safety, tolerability, and treatment compliance. The study plans to enroll 74 partecipants, with an enrollment period of about 11 months and a total study duration of approximately 12 months (from first partecipant first visit to last partecipant last visit).