Latanoprost Preserved Versus Unpreserved: Effect on Tear Film Thickness as Measured With OCT

Topical antihypertensive eye drops are a key element of modern antiglaucoma treatment. Most of these eye drops contain preservatives to allow for the use of multi-dose containers. In the recent years evidence has, however, accumulated that these preservatives may induce ocular surface disease (OSD). This is particularly true for the most widely used preservative, benzalkonium chloride (BAK). Whereas this is well documented in many in vitro and animal studies, evidence from clinical trials is sparse. The only randomized masked study that showed superiority is a pivotal company-sponsored study indicating improved tolerability and reduced hyperemia of unpreserved versus preserved latanoprost eye drops.

The investigators have recently introduced an optical coherence tomography (OCT) technology that provides a resolution as high as 1.2 µm for the human cornea. Using this technology the investigators were able to show that tear film thickness (TFT) is negatively correlated with symptoms of OSD. Changes in TFT can be assessed with very high sensitivity below the level of resolution as also evident from studies after administration of lubricants.

In the present study, the investigators hypothesize that switching glaucoma patients from preserved prostaglandin analogues to unpreserved latanoprost is associated with an increase in TFT as measured with OCT. As a control the investigators will use preserved latanoprost and the study hypothesis will be tested in a randomized, controlled, single-masked parallel group design. TFT is chosen as main outcome variable, standard measures for signs and symptoms of OSD are selected as secondary outcomes. The present study may provide valuable information on the superiority of unpreserved versus preserved therapy.