Lactate dehydrogenase activity in pathological human tears obtained with glass capillaries correlates with the albumin content.

Lactate dehydrogenase (LDH) activity was measured in stimulated normal human tears and in tears from patients suffering from various corneal and conjunctival disorders. In normal tears the LDH activity was below the detection level of the method used, and it was hardly detectable in tears of most of the patients. The LDH activity correlated with the serum albumin content (r = 0.745, n = 32), suggesting that its source in pathological cases could be the plasma by transudation, and not the surface epithelial cells. Based on these results, LDH activity cannot be used as a measure of epithelial cell destruction in most pathological conditions, since the tear secretion of the patients is usually stimulated due to irritation, associated with the disorder or disease.