There is very little information regarding systemic drug effects of aqueous tear production in humans. Studies in animals show an effect of autonomic nervous system drugs on tear production; clinical experience suggests that drugs with autonomic effects can alter tear production in humans. A variety of systemic medications taken by millions of patients with diverse disease (antihistamines, antispasmodics, anti-Parkinson drugs, cardiovascular agents, psychotropic drugs) have anticholinergic effects and seem to have an adverse effect on tear production. It is probable that these can produce keratoconjuctivitis sicca, at least in patients with marginally adequate tear secretion. This study will attempt to measure aqueous tear production in human subjects on such drugs by the use of serial Schirmer tests. In the case of drugs with minimal side effects, e.g., antihistamines, antispasmodics, volunteers will be recruited and the studies conducted in a double masked manner; in the case of the more potent drugs, patients about to be started on such agents will be examined with serial Schirmer tests prior to and after the onset of medication. Where this approach is not feasible, patients on the drugs will be studied and a group of age and sex matched normals will be used as controls.