Improvement of tear ferning patterns of artificial tears using dilute electrolyte solutions

Abstract

The purpose of the research was to examine how the addition of dilute solutions of sodium chloride (NaCl), potassium chloride (KCl), or a combination of the two would impact the tear ferning (TF) patterns in artificial tears. Artificial tears (1 μL) were mixed with solutions (1–7 μL) of NaCl, KCl, or both (10–30 mg), prepared in double-distilled water (100 mL), to produce homogenous mixtures. A sample (1 μL) of each mixture was dried on a microscopic glass slide at 20 °C and with less than 20% humidity. The TF patterns were inspected using a light microscope, graded, and compared with the corresponding TF grades of pure artificial tears. Significant improvements (Wilcoxon test, P = 0.001) in the TF grades of the artificial tears were observed after the addition of solutions of NaCl and KCl or a mixture of both. The TF grades of the artificial tears decreased after adding different volumes and concentrations of electrolyte solutions. Generally, NaCl was more efficient than KCl in improving such grades. The TF grades of Blink Contact Soothing Eye Drops and Refresh Plus Tears were noticeably improved compared to the other grades. For example, Blink Contact Soothing Eye Drops' TF grade improved from 1.7 to 0.6 when 6 μL of NaCl solution (30 mg/100 mL water) was added to 1 μL of the eye drops. When a mixture of NaCl and KCl (1:2; 5–7 μL; 30 mg each in 100 mL water) was added, the TF grade improved to 0.5. In conclusion, the TF test evaluated the effect of adding dilute electrolyte solutions to artificial tears in vitro. Adding dilute solutions of NaCl and KCl, or a mixture of both, significantly improved the TF grades of artificial tears.

Keywords

• Artificial tears
• Tear ferning grades
• Monovalent electrolytes
• Sodium and potassium chlorides
• In vitro tear ferning test