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Michael R. Wang, Hui Lu, Jianhua Wang, Meixiao Shen; Characterization of Hydrophilic Properties of Soft Contact Lenses Using Optical Reflectometer. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6537.
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To characterize soft contact lenses hydrophilic properties through non-contact evaluation of water film breakup dynamics using a new optical reflectometer method.
Optical reflectometer with an internal optical spectrometer is used to evaluate the water film thickness on several soft contact lenses. A Tungsten Halogen light source sends a broad band white light through a 200 µm diameter optical fiber and an achromatic lens to the water film/contact lens surface. The normal direction reflected light from the air/water film and water film/contact lens interfaces is collected by a receiving optical fiber connecting to the optical spectrometer to evaluate the wavelength dependent reflectance. The water film thickness is determined through curve fitting with predetermined contact lens and water refractive and absorption indices. In a water bath, the top of the contact lens is slightly emerged from the water surface. A drop of water to the contact lens forms a thin water film which is thinning as a function of time. The optical reflectometer evaluates the water film thinning dynamics and water film breakup thickness. The thinner the breakup water film thickness the better the hydrophilic performance of the contact lens.
Eight soft contact lenses have been evaluated in their water film dynamics and film breakup thicknesses. Videos of water film reflectance curves showing dynamic changes have been captured. Water film thicknesses have been evaluated as a function of time to reveal dynamic film thinning process. Water film thinning from estimated 7 µm to 800 nm has been demonstrated. Figure shows a captured water film wavelength dependent reflectance curve. Different contact lenses are found to offer different water film breakup thicknesses and thus different hydrophilic properties.
This study demonstrates the effective use of optical reflectometer for evaluation of water film dynamics on contact lens revealing hydrophilic properties of different contact lenses.
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