The "dry eye syndrome" DES is a highly prevalent ocular disease, in particular in the elderly
population. One mainstay of therapy for patients suffering from DES is the use of topically
administered lubricants. However, despite many efforts, no "ideal" formulation has yet been
Recently, Croma Pharma has introduced chitosan-N-acetylcysteine eye drops, designed for
treatment of symptoms related to DES. Chemically, chitosan is a polycationic biopolymer with
favourable biological properties such as high biocompatibility and low toxicity.
Additionally, the new formulation comprises N-acetylcysteine, which has been used in
ophthalmology because of its mucolytic properties for several years. Based on theoretical
considerations, one can hypothesize that the new chitosan derivative may show an increased
adhesion to mucins of the ocular surface and may therefore be particularly beneficial in
reducing the symptoms associated with DES. We have recently shown in a phase I trial that
single instillation of chitosan-N-acetylcysteine eye drops is well tolerated in young healthy
However, no data is yet available about safety and tolerability of chitosan-N-acetylcysteine
in subjects wearing contact lenses. This is of special interest because the tear film is
critical to successful contact lens wear. Disturbances of the quantity or quality of the tear
film results in intolerance of contact lens wear and possible damage to the ocular surface.
This trial seeks to investigate the local tolerability and possible ocular discomfort of
chitosan-N-acetylcysteine eye drops after repeated instillation .