Raman point mapping of tear ferning patterns - art. no. 685309

This study attempts to combine the tear ferning test and the drop coating deposition Raman spectroscopy (DCDRS) technique to analyze the biochemical composition of human tear fluid from healthy volunteers. DCDRS has been shown to be a highly reproducible and sensitive method of obtaining Raman spectra from low concentration protein solutions making it ideal for the analysis of tear fluid. On drying, tear samples were found to produce ring-shaped patterns, which are characteristic of the DCDRS technique, with additional fern-like structures produced inside the rings. The biochemical composition of the each drying pattern was studied by Raman point mapping and principal components analysis. Assignment of high-signal-to-noise tear spectra showed that tear proteins, urea, bicarbonate and lipid components were all present in the dried tear drop. Comparing an image time series of the drying process with the biochemical distributions from the Raman point map revealed the order of biochemical deposition in the drying pattern. The combination of DCDRS and the tear ferning test shows enough promise to be further studied as a near-patient technique for assisting the diagnosis of ocular infection, but further work is required to validate the technique.