A Study on the Effect of Changing From Preserved Prostaglandin Formulations to Preservative Free Tafluprost on Tear Film Thickness

Inclusion Criteria: * Men and women aged over 18 years * Diagnosed primary open angle glaucoma treated with preserved prostaglandins for at least 6 months OR * Patients with ocular hypertension treated with preserved prostaglandins for at least 6 months * IOP ≤ 21 mmHg in the study eye at the screening examination (under treatment) * Mean TFT at the screening visit ≤ 6µm in the study eye * At least 2 symptoms of dry eye syndrome in the study eye (itching, stinging, blurred vision, foreign body sensation, debris, conjunctival redness) since at least one month * Tear break up time ≤ 10sec Exclusion Criteria: * Participation in a clinical trial in the 3 weeks before the screening visit * Severe visual field loss as defined as an MD of -15 or worse in the study eye * Symptoms of a clinically relevant illness in the 3 weeks before the first study day * Presence or history of a severe medical condition that will interfere with the study aim as judged by the clinical investigator * Sjögren's syndrome * Stevens-Johnson syndrome * Presence or history of a severe ocular condition that will interfere with the study aim as judged by the clinical investigator * Presence or history of allergic conjunctivitis * Treatment with corticosteroids in the 4 weeks preceding the study * Wearing of contact lenses * Topical treatment with any ophthalmic drug in the 4 weeks preceding the study except glaucoma medication or topical lubricants * Ocular infection * Ocular surgery in the 6 months preceding the study (except laser trabeculoplasty) * Pregnancy, planned pregnancy or lactating * Contraindication against the use of topical prostaglandin therapy