Objectives: To assess material properties that affect preservative uptake by silicone hydrogel lenses.
Methods: We evaluated the water content (using differential scanning calorimetry), effective pore size (using probe penetration), and preservative uptake (using high-performance liquid chromatography with spectrophotometric detection) of silicone and conventional hydrogel soft contact lenses.
Results: Lenses grouped similarly based on freezable water content as they did based on total water content. Evaluation of the effective pore size highlighted potential differences between the surface-treated and non–surface-treated materials. The water content of the lens materials and ionic charge are associated with the degree of preservative uptake.
Conclusions: The current grouping system for testing contact lens–solution interactions separates all silicone hydrogels from conventional hydrogel contact lenses. However, not all silicone hydrogel lenses interact similarly with the same contact lens solution. Based upon the results of our research, we propose that the same material characteristics used to group conventional hydrogel lenses, water content and ionic charge, can also be used to predict uptake of hydrophilic preservatives for silicone hydrogel lenses. In addition, the hydrophobicity of silicone hydrogel contact lenses, although not investigated here, is a unique contact lens material property that should be evaluated for the uptake of relatively hydrophobic preservatives and tear components.
Division of Ophthalmic, Neurological and Ear, Nose and Throat Devices (J.A.G., J.C.H., E.M.R., M.B.E.), Office of Device Evaluation, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, MD; Division of Chemistry and Materials Science (K.S.P.), Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, MD; Division of Biology (V.M.H., A.D.L., M.E.S.), Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, MD.
Address correspondence and reprint requests to Malvina B. Eydelman, M.D., 10903 New Hampshire Ave., WO-66, Room 2410, Silver Spring 20993, MD; e-mail: email@example.com
The Food and Drug Administration funded this work.
Authors have no commercial financial support or conflicts of interest to disclose.
The mention of commercial products, their sources, or their use in connection with material reported herein is not to be construed as either an actual or implied endorsement of such products by the Department of Health and Human Services.
The authors J. Angelo Green and K. Scott Phillips contributed equally.
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Accepted September 4, 2012