Effect of nonisotonic solutions on tear film osmolality.

We found that the original osmolality of the tear film is regained rapidly subsequent to the installation of hypotonic artificial tears or other nonisotonic solutions. The minor irritation due to nonisotonicity and the increased tear volume both contribute to the increased turnover rate which in turn results in the short half-life (measured in seconds) of these solutions in the eye. Despite the expected fluctuation in tear volume and probably in tear secretion rate during the experiment, the osmolality of the tears followed an exponential decay with relatively good correlation.