[The effect of the method of collecting lacrimal fluid on its composition]

The authors have examined the relationship between the technique of the tear collection and the lacrimal enzymes activity. The studies have revealed that lactate dehydrogenase (LDH) appears in the tears of normal subjects only if the tears are collected by mechanically affecting the cornea and the conjunctiva. Microinjuries of the corneal epithelium result in LDH release into the tears. If the tear is collected from the cheek after ammonium hydroxide inhalation, it contains no LDH. The activities of the lacrimal acid and alkaline phosphatases do not vary when collected by different methods. Therefore, the method for the tear collection should be taken into consideration when interpreting the results of biochemical analyses.