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J. Liu, X. He, C.J. Roberts; Validation of Ultrasonic Measurements of Corneal Phantoms . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1361.
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© ARVO (1962-2015); The Authors (2016-present)
Non–invasive measurement of biomechanical properties of corneas may provide important information for ocular disease detection and management. We have reported a model and system based on ultrasound for in vivo determination of corneal biomechanical properties. In this study we tested the sensitivity of the approach in differentiating three material types of soft contact lenses as corneal phantoms. We further validated the ultrasonic measurements with the results obtained from other independent measurements.
Three material types of soft contact lenses were obtained (six lenses in each group) and measured using a broadband ultrasound transducer (10 MHz, XMS, Panametrics–NDT). The ultrasonic reflections from the contact lenses were recorded by a 500 MHz/8–bit digitizer (Acqiris, DP105), and displayed and processed by a PC. A reference signal was recorded to compute the normalized power spectra using Fast Fourier Transformation. An inverse algorithm based on simplex method was used to reconstruct three parameters of the contact lenses: density, thickness, and elastic constants. The thickness for each lens was then measured by an electronic thickness gauge (ET–3, Rehder). The density for each group of lenses was determined using Archimedes’ principle by comparing the mass in air and in saline. These results were compared to the results from the ultrasonic reconstruction.
The ultrasound system was able to differentiate the elastic constants of the three material types of the soft contact lenses with a P–value<0.001. The reconstructed thickness and density agreed well with the standard measurements.
Our results indicated that the ultrasonic system was sensitive and accurate in measuring the material properties of cornea phantoms. It is important to verify the feasibility of the system under in vivo settings.
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