A quantitative method for LDH, MDH and albumin levels in tears with ocular surface toxicity scored by Draize criteria in rabbit eyes.

We have established a quantitative method for evaluation of ocular surface lesions on the basis of lactate dehydrogenase (LDH) activity, malate dehydrogenase (MDH) activity, and albumin levels in rabbit tears. Lesions were produced with solutions of 0.005-0.02% benzalkonium chloride (BAK), 0.01-0.03% chlorhexidine digluconate (CHX), and 0.01-0.03% polyhexamethylene biguanide hydrochloride (PHMB), all of which are widely used in topical ophthalmic preparations. Two drops of test solution were instilled 15 times into rabbit eyes at 5 minute intervals. Sixty minutes after 0.02% BAK instillation, tear LDH activity increased from 1,840 U/L (without instillation) to 26,100 U/L, and concomitantly tear albumin levels rose from 0.11 mg/mL (without instillation) to 9.48 mg/mL. Instillation of 0.03% CHX and 0.03% PHMB caused smaller increases in LDH and MDH activity and albumin tear levels. LDH activity and albumin levels in tears were significantly correlated with the degree of total ocular surface lesions in both cornea and conjunctiva as observed by slit lamp biomicroscopy quantified using a modified Draize score. Based on the results of this study, we believe that LDH activity and albumin level in tears can be used as objective indicators for the quantitative evaluation of ocular surface lesions on both cornea and conjunctiva following application of topical ophthalmic preparations containing cytotoxic preservatives in animals and man.