Tear Lab is an instrument that measures tears osmolarity, that is the quantity of liquefied solutes in tears.
It’s a marker of the inflammatory state of ocular surface.
While patient is looking at a point straight on the opposite wall, the operator puts a device on the edge of the lower eyelid, to collect a tear sample. Then the operator puts the device in the instrument which analyzes tear sample and supplies a value in milliosmoli/litre.
Values over 290mOsM/L indicate existence of inflammatory state and the difference of 10 mOsM/L or more between one eye and the other one too.