Osmotic adaptation to rigid contact lenses.

Using a precision thermocouple hygrometer, requiring just 5 microliters of sample, the tear osmotic pressures of 6 subjects were monitored throughout their adaptation to rigid contact lenses. Relative to the prefitting baselines established for each previous to this study, these subjects showed a range of hypotonic shifts on initially receiving their lenses, but this imbalance was rectified by the end of the first wearing week and a new relatively hypertonic level of tear osmotic pressure was commonly established. This new baseline was reflected in the pre-insertion samples of several of the subjects as well once adaptation was advanced.