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R D. Johnson, David B. Bennett, Zachary D. Taylor, Jean P. Hubschman, Daniel Sassoon, Priyamvada Tewari, Martin Culjat, Elliott Brown, Raul S. Singh, Warren S. Grundfest; Novel Corneal Hydration Imaging Technology Using Terahertz Illumination. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4092.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the ability of imaging systems based on Terahertz illumination to measure corneal hydration.
9 ex vivo porcine corneas were soaked in a 0%, 3%, 5%, and 7% polyethylene glycol (PEG) solutions containing 0.15M NaCL for 3 days to produce corneas with water concentrations from 79.1% to 91.5% by volume. These tissues were then imaged using a Terahertz imaging system with an illumination frequency centered at 525 GHz ( = 570 µm)
A clear and consistent decrease in reflected THz intensity is seen in the corneas with reduced amounts of absorbed water. The hydration sensitivity (observed change in THz reflectivity for a given change in water concentration) calculated with calibration targets was 0.190% by volume. The THz imaging system provided a spatial resolution of ~ 1 mm enabling imaging of the cornea based on hydration.
The increase or decrease of corneal hydration in several pathologies may impair its transparency. Currently, the only way to monitor corneal edema is through qualitative visual observation or indirect evaluation by serial quantitative thickness measurements. Terahertz illumination is a novel technology, which demonstrated its ability to assess corneal hydration and to clearly differentiate hydration status of ex vivo corneal tissue with very high sensitivity. The potential applications of this new imaging modality in the measurement and monitoring of corneal hydration in various pathologic corneal states may be promising.
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