Long term treatment with anti-glaucomatous drugs has been shown to increase the incidence of dry eye syndrome with all known consequences such as ocular discomfort and epithelial keratitis. Given that thinning of the tear film appears to be a risk factor for the development or the aggravation of dry eye syndrome, the current study seeks to investigate whether tear film thickness is changed after topical treatment with anti-glaucomatous drugs in healthy subjects.

For this purpose, tear film thickness will be measured at baseline and after single instillation of one of 5 study drugs in one randomly chosen eye. In addition, one group of 20 subjects will receive no drug and will serve as a second control. Drug effects on tear film thickness will be compared to the fellow, non-treated eye. In addition, effects on tear film thickness of timolol with preservatives (Timoptic 0.5%) will be compared to timolol without preservatives (Timophtal sine 0.5%) and three lubricants with different viscosity (Genteal HA, Hylo-Comod, Thealoz).

Inclusion Criteria:

• Men and women aged over 18 years
• Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant
• Normal ophthalmic findings, ametropia < 6 Dpt.

Exclusion Criteria:

• Regular use of medication (except contraceptives), abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study
• Treatment in the previous 3 weeks with any drug
• Symptoms of a clinically relevant illness in the 3 weeks before the first study day
• Patients with known hypersensitivity to the study drug or any ingredients
• History or current COPD or asthma
• AV-block grade II or more
• Ametropy ≥ 6 Dpt
• Pregnancy