Use of tear enzyme activities to assess the corneal response to contact lens wear.

A non-invasive biochemical method for assessing the effects of contact lens wear on the in vivo corneal epithelium is described. A fluorometric technique is used to measure the activities of lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) in human tear fluid. In view of the corneal epithelial origin of these enzymes, changes in their activity can indicate the severity of environmental stresses on the corneal epithelium. Following short-term wear of contact lenses, LDH and MDH activities are altered so that the tear LDH/MDH ratio is elevated. The magnitude and time course of this elevation are influenced by contact lens type, fit and duration of wear. The technique can yield more specific measures of the corneal response to contact lens wear than previous techniques.