Fluorescence Lifetime Based Corneal Metabolic Imaging

We are developing a time-gated fluorescence lifetime imaging microscopy (FLIM) instrument for in vivo metabolic imaging of corneal tissues, based on the fluorescence of metabolic co-factor FAD. Here we report on the first results of this project, namely on ex vivo measurements done with a time correlated single photon counting FLIM instrument, and on the first measurements done with the time-gated microscope prototype. Ex-vivo measurements with rat corneas show that it is possible to image FAD fluorescence from corneal epithelial layer and to obtain information from its fluorescence decay parameters that correlates to their metabolic activity. Measurements with test-targets and fluorescence lifetime standards show that the prototype of the time-gated fluorescence lifetime microscope for in vivo FAD imaging has the precision and the accuracy, as well as the timing and lateral spatial resolutions, required for such measurements.