Ocular lubrication

Lubricants are the mainstay of dry eye treatment. Whereas they do not target the disease itself they relief from the symptoms associated with both tear-deficient and hyper-evaporative dry eye. The duration of action of lubricants critically depends on the residence time at the ocular surface. This is influenced by the viscosity of the eyedrops, their charge, but also by their ability to bind to mucins. Residence time of drugs at the ocular surface has traditionally been investigated using radio-active labelling of the drugs. This does, however, have several drawbacks. Labelling changes the molecule thereby potentially changing the residence time. In addition, experiments are costly and require significant experimental effort. We have developed a technique that is capable of measuring tear film thickness using a custom-built OCT. With this device it is possible to get insight into the residence time of topically administered lubricants. Data for hyaluronic acid, osmoprotective substances and chitosan thiomer are presented.