Vitamin C levels in human tears
C. A. Paterson and M. C. O'Rourke
Human tears, collected using the Schirmer strip method, were analyzed by
high-performance liquid chromatography for vitamin C (ascorbic acid). In
"basal" tears, the levels of ascorbic acid ranged from 3.9 to 23 mg/dL (220
to 1310 mumol/L); lower values correlated with higher tear flow rates. In
reflex tears, induced by brief ammonia inhalation, the ascorbic acid level
fell dramatically and appeared to reach a minimum level around 2 mg/dL (110
mumol/L). Even the low level in reflex tears, however, was consistently
higher than plasma levels. Ascorbic acid in tears has a potential
anti-inflammatory role.
