Abstract
Purpose:
Lipid deposits are responsible for dewetting of contact lens surfaces, leading to instability of the tear film and possible contact lens related dry eyes and discomfort. The purpose of this work was to develop a novel method to visualize and characterize lipid deposits on soft contact lens surfaces.
Methods:
Five silicone hydrogel lenses and one hydrogel lens (etafilcon A) were soaked in cholesteryl oleate solution (5.6 mg/ml) overnight for 12 hours. For each lens type, a group consisting of five lenses was then stained with Oil Red O and imaged under fluorescence microscopy with a DeltaVision Spectris Core microscope running softWoRx 1.0 software. The central 2 mm diameter zone of each stained lens was imaged at 100X magnification and the total surface area of lipid deposition within the selected frame of 4400 µm2 was calculated using ImageJ 1.47 software. Images were compared quantitatively in terms of median and range (minimum - maximum) of lipid deposition surface areas (μm2) on the various types of contact lenses.
Results:
Cholesteryl oleate deposits were successfully stained by Oil Red O on all contact lens material types, clearly visible at 100X magnification. The median and range of areas of deposition for each of the materials was as follows: balafilcon A (6.40 μm2, 0-182.11 μm2), narafilcon A (1.61μm2, 0-9.36μm2), etafilcon A (1.56μm2, 0-147.66μm2), delefilcon A (0.983μm2, 0-28.81μm2), enfilcon A (0.12μm2, 0-36μm2), lotrafilcon A (0μm2, 0-8.58μm2). There was no statistically significant difference in the median ranked areas of lipid deposition on various types of lenses (Kruskal-Wallis test, p = 0.88).
Conclusions:
Lipid deposits on a contact lens can be imaged in vitro with Deltavision microscope using the fluorescent dye Oil Red O and high magnification (100X). Surface coverage of lipids is typically small and similar at the central 2 mm region among the various lens materials examined. In vitro imaging of lipid deposits may help improve our understanding of deposits and how they affect tear film coverage over a contact lens surface.
Keywords: 477 contact lens •
583 lipids •
551 imaging/image analysis: non-clinical