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.