Abstract
Purpose: :
There is a significant interest in the total amount and types of lipids in the tear film since disruption of the lipid layer is thought to decrease tear film stability and cause dry eye. There is still much clinical uncertainty as to how a soft contact lens alters the lipid layer of the tear film. The purpose of this study is to determine Nile Red and Oil Red O’s ability to detect the deposition of a common tear film lipid on lotrafilcon A lenses.
Methods: :
Eight unworn lotrafilcon A lenses were individually soaked in successively decreasing amounts of cholesterol oleate solution (5.6 mg/mL to 0.00 mg/mL) for one day in triplicate for each staining procedure. The sets of lenses were then stained with Nile Red or Oil Red O. The lenses were then individually visualized with a Nikon Eclipse 80i florescent microscope at 100x magnification, and two representative photos were taken of each lens.
Results: :
Nile Red gave a robust number of stained lipid deposits on the lenses soaked in 5.60 mg/mL cholesterol oleate solution and variable yet decreasing amounts of staining were detected at lipid concentrations greater than 0.09 mg/mL when compared to the negative control lenses. Staining was detected on all lenses at all concentrations of lipid with staining being found on half of the negative control lenses. Oil Red O gave a robust number of stained lipid deposits on the lenses soaked in 5.60 mg/mL lipid solution; approximately 25% the number of deposits were detected at 1.40 mg/mL when compared to 5.6 mg/mL, and approximately 25% the number of deposits were detected at 0.35 mg/mL when compared to 1.40 mg/mL. Lipids were not detected when lenses were incubated at concentrations of lipid solution of 0.09, 0.02, 0.01, or 0.00 (mg/mL). Rare staining was seen on the negative control lenses.
Conclusions: :
Nile Red is able to detect lipid on lenses when they have been incubated in concentrations of lipid solution greater than or equal to 0.09 mg/mL while Oil Red O is able to detect lipid on lenses when they have been incubated in concentrations greater than or equal to 0.35 mg/mL. Oil Red O might make a better stain than Nile Red for silicone hydrogel lenses due to its superior image quality.
Keywords: contact lens • lipids • cornea: tears/tear film/dry eye