Effect of monovalent electrolyte solutions on the human tear ferning pattern.

Purpose: To investigate the effect of the addition of a low concentration of sodium chloride (NaCl) and potassium chloride (KCl) solutions on the tear ferning (TF) patterns of tears collected from humans.

Methods: A tear sample (20 μL) was collected from the right eye of 23 males and 7 females (25.4 ± 6.