Tear fluid osmolarity as a potential marker of hydration status.

Unlabelled: It has been suggested that tear fluid is isotonic with plasma, and plasma osmolality (P(osm)) is an accepted, albeit invasive, hydration marker. Our aim was to determine whether tear fluid osmolarity (T(osm)) assessed using a new, portable, noninvasive, rapid collection and measurement device tracks hydration.

Purpose: This study aimed to compare changes in T(osm) and another widely used noninvasive marker, urine specific gravity (USG), with changes in P(osm) during hypertonic-hypovolemia.