Biomarkers for Detection of In Vitro Ocular Irritancy

Exposure of rabbit corneas to nanosecond pulse width 1540 nm infrared laser light produced a less severe coagulative necrosis when compared to millisecond pulse width exposures. We expected this result because nanosecond pulse widths should have less of a photothermal effect than millisecond pulse widths. Matrix Metalloproteinase-2 MMP-2 immunohistochemistry was used to detect if subtle stromal remodeling had occurred. We found a markedly increased MMP-2 immunohistochemical pattern than what we would have predicted from the HE stains alone. Approximately half of the beam path was filled with MMP-2 reaction product. As far as we know this is the first analysis comparing the stromal remodeling effects of an infrared laser operating in both the millisecond and nanosecond pulse widths. This finding is important to the AFOSR mission because it demonstrates that significant tissue changes associated with comeal wound healing can occur following exposure to nanosecond laser pulse widths that are not detectable with standard histologic techniques.