Tear film, pharmacology of eyedrops, and toxicity

Objective methods are now available to more effectively evaluate the dry eye and the surface toxicity associated with ophthalmic preparations and contact lens wear. Tear osmolarity, ocular surface evaporation, fluorophotometric tear flow, and meibomian gland imaging can be used to assess the dry eye state. Studies have demonstrated that evaporation plays a greater role in most dry eye conditions than was previously estimated. Tear protein analysis for lactate dehydrogenase, malate dehydrogenase, and albumin levels can be used as markers for epithelial cell toxicity and can be combined with tandem scanning confocal microscopy of the epithelium to demonstrate and quantify changes in epithelium morphology and function due to contact lens wear and ophthalmic medications.