Use of in vivo confocal microscopy to understand the pathology of accidental ocular irritation

In vivo confocal microscopy (CM) provides a unique ability to section optic ally through living, intact tissues and organs to characterize qualitativel y and quantitatively pathological changes in 4 dimensions (x, y, and z, and time). It involves the capture of realtime images without the need for exc ision, fixation and processing. In vivo CM principally has been used for ev aluation of eyes in patients and laboratory animals but has potential appli cation to studies of other tissues/organs. In vivo CM is being used in huma n ophthalmology clinics. It has been used as a research tool for quantitati ve, in situ measurement of corneal wound contraction, fibroblast migration, corneal endothelial cell migration, corneal epithelial cell size and desqu amation following contact lens wear and surgery, and the assessment of corn eal surface toxicity following application of commonly used ophthalmic pres ervatives. In vivo CM allows us to (a) characterize changes to a light micr oscopic (i.e., cellular) level; (b) quantify changes objectively; (c) condu ct studies of injury and repair in the same animal and directly correlate m icroscopic changes to clinical observations over time as this technique is used in the living animal: and (d) conduct comparative studies in humans. H ere we present a brief overview of in vivo CM and how we are using it to pr ovide noninvasive, in situ qualitative and quantitative histopathologic cha racterization of accidental ocular irritation. Our intent is to provide an awareness of this relatively new methodology and one practical application of its use in research. The goal of our work is to provide objective, quant itiative data for use in developing and validating mechanistically based in vitro replacement tests.