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D. Borja, R. Pertaub, H. Loree, D. Muller; Correction of Myopia With Thermal Treatment of Anterior Cornea: Results With ex vivo Porcine Model. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4216.
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To characterize the change in shape and refractive power of ex vivo porcine corneas after Keraflex (KFX), a microwave-based approach to thermal keratoplasty for myopic correction.
Annular thermal lesions were induced on the anterior corneas of 27 fresh ex vivo porcine globes (post mortem time < 1day). KFX was performed with a 4.5 mm inner dia. x 200 µm thick inner diameter electrode and a 6.5 mm outer dia. coaxial ground electrode with microwave frequency of 915MHz and energies of 1-8J. The geometry of the thermal lesion and the refractive power change due to anterior cornea shape change were assessed from pre- and post-KFX cross sectional Scheimpflug slit-lamp images acquired along 32 meridians. The anterior corneal surface profiles were obtained from each image and fit with a conic section function to determine radii of curvature and asphericity. The SimK refractive power of the anterior cornea pre- and post-KFX was calculated using the instantaneous radius of curvature over an 8mm pupil diameter.
Stromal shrinkage occurred below the inner electrode. Approximate lesion depth (LD) increased linearly with energy (LD [µm] = 19.6+23.4 [µm/J] * Energy [J], r=0.72 and p<0.0001) as did the change in anterior corneal surface refractive power (ΔPower [D] = -0.75 + 1.01 [D/J]* Energy [J], r=0.85 and p<0.0001).
In an ex vivo porcine cornea model, KFX flattens the shape of the anterior cornea, which reduces its refractive power and can correct for myopia. The extent of corneal flattening is a linear function of applied energy. These results are qualitatively similar to those of previous human studies of KFX (unpublished), suggesting that this ex vivo model is a useful tool for optimization of the clinical KFX treatment.
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