Lactate dehydrogenase levels and isoenzyme patterns in the serum and aqueous humor of adult cataract patients. 
Serum and aqueous humor lactate dehydrogenase (LDH) levels were assayed in 46 patients with senile cataracts at the time of cataract extraction.  The mean aqueous level was 37 IU/liter and the mean serum level 152 IU/liter.  In each case, the serum LDH level was higher than the corresponding aqueous LDH.  The LDH isoenzyme levels were also determined; LDH 4 and LDH 5 were elevated in cataract aqueous samples, while the serum isoenzymes were normal.  The LDH studies of normal and diseased globes must be rigorously standardized to avoid artificially high or low levels.