In vivo thickness measurement of the lipid layer and the overall tear film by interferometry

New approaches for the simultaneous measurement of the thickness of the lipid layer (LL) and overall tear film (TF) in vivo are needed. In the current research, the interference signal from the ocular surface was analyzed and simplified as the superposition of two sinusoidal functions. One function with low frequency was modulated by LL, and the other function with high frequency was modulated by precorneal TF (PCTF). Two sinusoidal functions were separated and analyzed to retrieve the thickness of LL and PCTF. To validate the feasibility of the approach, a customized fiber-based interferometer with a related data processing program was developed and tested in vivo.