Abstract: Apparatuses and methods employing ocular surface interferometry (OSI) employing polarization and subtraction for imaging, processing, and/or displaying an ocular tear film are disclosed. The apparatuses and methods can be employed for measuring tear film layer thickness (TFLT) of the ocular tear film, which includes lipid layer thickness (LLT) and/or aqueous layer thickness (ALT). An imaging device is focused on the lipid layer of the tear film to capture optical wave interference interactions of specularly reflected light from the tear film combined with a background signal(s) in a first image. The imaging device is focused on the lipid layer of the tear film to capture a second image containing background signal(s) in the first image. The second image can be subtracted from the first image to reduce and/or eliminate background signal(s) in the first image to produce a resulting image that can be analyzed to measure tear film layer thickness (TFLT).