Dry Eye Syndrome (DES) is a common condition that affects approximately 20% of adults aged 45 and older. Although several clinical tests for the diagnosis and monitoring of DES are available, currently no gold standard for the assessment of DES exists. It has, however, been hypothesized that the assessment of tear film osmolarity may be a new and promising approach of an objective and non-invasive method for diagnosis and monitoring of treatment success.

Recently, a new commercially available instrument (TearLab®, OcuSens Inc, San Diego, USA) for the assessment of tear film osmolarity has been introduced. This instrument allows for the easy and non-invasive determination of tear film osmolarity. Unfortunately, no data about reproducibility are yet available. Consequently, the current study sets out to investigate the short time reproducibility of tear film osmolarity measurements using the TearLab® instrument.

Inclusion Criteria:

Patients with dry eye syndrome (DES):

• Men and Women aged between 45 and 80 years, with DES defined as a pathological Schirmer I test and / or a pathological break-up time test. Schirmer I test and break up time will be tested and analyzed according to the guidelines published in the Report of the International Dry EyeWorkShop (DEWS) 2007
• normal findings in the ophthalmic examination other than DES

Healthy control group:

• Men and Women aged between 45 and 80 years,
• normal findings in the medical history and ophthalmic examination

Exclusion Criteria:

• Abuse of drugs or alcoholic beverages
• Participation in a clinical trial
• Symptoms of a clinically relevant illness