Dopamine levels in human tear fluid.

PURPOSE: To determine the levels of dopamine in tear fluid and demonstrate the use of tear fluid as a non-invasive source for dopamine measurements in humans.

METHODS

The study cohort included 30 clinically healthy individuals without any pre-existing ocular or systemic conditions. Matched tear fluid (using Schirmer's strips and capillary tubes) and plasma were collected from the subjects. Dopamine levels were evaluated using direct competitive chemiluminescent enzyme-linked immunosorbent assay (ELISA), dopamine kit (Cloud Clone Corp, TX, USA).

RESULTS

Significantly higher dopamine levels were found in the tear fluid compared to plasma in the study subjects. The level of dopamine was 97.2 ± 11.80 pg/ml (mean ± SEM), 279 ± 14.8 pg/ml (mean ± SEM), and 470.4 ± 37.64 pg/ml (mean ± SEM) in the plasma and in the tears collected using Schirmer's strips and capillary tubes, respectively.

CONCLUSION

Dopamine was detectable in all the tear fluid samples tested and was also found to be at a higher concentration than in plasma samples. Tear fluid can be used as a non-invasive sample source to monitor dopamine levels.