Studies have shown that ocular surface disease (OSD) is common among patients with glaucoma with a prevalence of 50% or more. The percentage of affected patients appears to increase with increasing number of topical anti-glaucoma products instilled. Both pre-clinical and clinical work has indicated that the preservatives used in anti-glaucoma drops, particularly benzalkonium chloride, are mainly responsible for this detrimental effect. As such more and more anti-glaucoma drugs without preservatives entered the market.

To prove that switching from preserved to unpreserved antiglaucoma medication improves the signs and symptom of OSD is, however, not easy. This is on the one hand related to the physiological variability of these parameters over time and on the other hand to the poor association between signs and symptoms. Recently, a new method for measuring tear film thickness (TFT) using ultra-high resolution optical coherence tomography (OCT) has been introduced. Using this method, it has been shown that there is a correlation between reduced TFT and OSD symptoms. In the present study, it is hypothesized that changing patients who are on preserved prostaglandin formulations to preservative free tafluprost may be associated with an increase in TFT.

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