At the Intensive Care Unit of the Onze Lieve Vrouwe Gasthuis, Amsterdam, light therapy is used by nurses for optimizing the light intensity in their work environment, for their own well being and for the prevention of sleep disturbances. The light therapy is also randomly used for the treatment of Intensive Care patients, though the effectiveness and functionality have not been a subject of investigation. Our purpose of this study is to determine whether bright light therapy is effective for reducing the incidence and the duration of delirium in the Intensive Care Unit. The primary outcome of this study is the duration of delirium, defined in number of days. This will be derived from the clinical assessments and the CAM-scores, performed by the trained non-clinician.