Calcium in tears and contact lens wear.

Tear calcium levels were measured in 27 normal subjects. An instrumental technique that required only 5- to 10-microL tear samples was used for this purpose. A mean of 2.11 +/- 49 (SD) mg/dl of calcium with a range of 1.05 to 3.49 mg/dl was determined for 67 tear samples from 27 subjects. This is in excellent agreement with more elaborate and previous methods. Various factors involved in tear calcium levels were also studied. Tear calcium levels were not significantly affected by the normal walking-hour wear of either hard or soft contact lenses among 22 women aged 19 to 35 years. Tear calcium day-to-day and diurnal variations were found for five of five subjects in a three-day study. Further studies of these variable phenomena are indicated.