12 February 2009 Numerical model and analysis of an energy-based system using microwaves for vision correction
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Abstract
A treatment system was developed utilizing a microwave-based procedure capable of treating myopia and offering a less invasive alternative to laser vision correction without cutting the eye. Microwave thermal treatment elevates the temperature of the paracentral stroma of the cornea to create a predictable refractive change while preserving the epithelium and deeper structures of the eye. A pattern of shrinkage outside of the optical zone may be sufficient to flatten the central cornea. A numerical model was set up to investigate both the electromagnetic field and the resultant transient temperature distribution. A finite element model of the eye was created and the axisymmetric distribution of temperature calculated to characterize the combination of controlled power deposition combined with surface cooling to spare the epithelium, yet shrink the cornea, in a circularly symmetric fashion. The model variables included microwave power levels and pulse width, cooling timing, dielectric material and thickness, and electrode configuration and gap. Results showed that power is totally contained within the cornea and no significant temperature rise was found outside the anterior cornea, due to the near-field design of the applicator and limited thermal conduction with the short on-time. Target isothermal regions were plotted as a result of common energy parameters along with a variety of electrode shapes and sizes, which were compared. Dose plots showed the relationship between energy and target isothermic regions.
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Radha Pertaub, Thomas P. Ryan, "Numerical model and analysis of an energy-based system using microwaves for vision correction", Proc. SPIE 7181, Energy-based Treatment of Tissue and Assessment V, 718105 (12 February 2009); doi: 10.1117/12.811154; https://doi.org/10.1117/12.811154
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