[Age-related alteration of tear dynamics in normal volunteers]

Age-related alteration of tear dynamics was studied using a newly developed fluorophotometer. The subjects, 55 eyes of 30 normal volunteers, included 32 eyes of 16 younger subjects in their twenties and 23 eyes of 14 older subjects aged 50 years and above. After instillation of 1 microliter of fluorescein solution at a concentration of 50 micrograms/ml into the temporal bulbar conjunctiva, fluorescence intensity was measured with the fluorophotometer every minute for 10 minutes after instillation. Fluorescein concentration was calculated from the intensity, and various parameters of tear dynamics were analyzed. In the younger subjects, the tear volume, initial turnover rate and basal turnover rate were 10.6 +/- 6.0 microliters, 37. 1 +/- 15.6%/min, and 25.8 +/- 15.2%/min, respectively. In the older subjects, these values were 6.5 +/- 2.6 microliters, 26.5 +/- 11.4%/min, and 20.5 +/- 13.5%/min, respectively. The basic tear flow rate, calculated from the basal turnover rate and tear volume, was 2.7 +/- 2.2 microliters/min in the younger and 1.4 +/- 1.0 microliter/min in the older subjects. There was a statistically significant difference in the tear volume, tear turnover rate, and basic tear flow rate between the younger and older subjects.