Influence of Lachrymal Substitutes on Tear Film Thickness in Patients With Moderate Dry Eye Syndrome

Inclusion Criteria: * Men and women aged over 18 years * Signed and dated written informed consent. * History of dry eye syndrome for at least 3 months * Tear Break Up Time (BUT) ≤ 10 seconds or Schirmer I test ≤ 5 mm and ≥ 2mm * OSDI (Ocular Surface Disease Index) ≤ 32 and ≥ 13 * Normal ophthalmic findings except dry eye syndrome, ametropia \< 6 Dpt. * No administration of topical lubricants 24 hours before the screening examination Exclusion Criteria: * Participation in a clinical trial in the 3 weeks preceding the study * Symptoms of a clinically relevant illness in the 3 weeks before the first study day * Presence or history of a severe medical condition as judged by the clinical investigator * Intake of parasympathomimetic or anti-psychotic drugs * Wearing of contact lenses * Glaucoma * Treatment with corticosteroids in the 4 weeks preceding the study * Topical treatment with any ophthalmic drug except topical lubricants in the 4 weeks preceding the study * Ocular infection or clinically significant inflammation * Ocular surgery in the 3 months preceding the study * Sjögren's syndrome * Stevens-Johnson syndrome * History of allergic conjunctivitis * Ametropia \>= 6 Dpt * Pregnancy, planned pregnancy or lactating * Known hypersensitivity to any component of the study medication. * Any medical or surgical history, disorder or disease such as acute or chronic severe organic disease * Inability to understand the study procedures