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E. M. Meisler, A. Sinha Roy, W. J. Dupps, Jr., D. M. Meisler; A Method for Computing Graft-Host Interface Curvature for Analysis of Refractive Shift in Endothelial Keratoplasty. Invest. Ophthalmol. Vis. Sci. 2010;51(13):770.
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© ARVO (1962-2015); The Authors (2016-present)
A Method for Computing Graft-Host Interface Curvature for Analysis of Refractive Shift in Endothelial Keratoplasty
Post-operative Scheimpflug-based anterior surface elevation maps of the cornea were obtained 3 months after DSAEK. High resolution OCT images of the horizontal corneal meridian were obtained for thickness measurements (Optovue Inc.). The OCT provided automatic segmentation tracings of the anterior surface of the host cornea and posterior surface of the graft. The graft-host interface was then traced using the software measurement tool at multiple locations along the radius. To calculate elevation, a polynomial was fit to the anterior corneal surface and normals at different radii (R) were calculated. Then, the thickness of the cornea and graft at each radius R was resolved along the normals to obtain the 2-D coordinates of the graft-host interface and posterior graft surface. The coordinates of the graft-host interface and posterior graft surface were fit both with polynomial and cubic spline methods, and tangential curvature was calculated from each of the surfaces. Results of the anterior and posterior corneal surfaces were compared with Scheimpflug curvature measurements along the horizontal meridian.
Figure 1 shows the manual segmentation of the surfaces along one meridian. Reconstruction of the surfaces beginning with anterior surface elevation and adding thickness data from OCT provides shapes of the different surfaces in Figure 2. In Figure 3, a comparison of tangential curvatures is shown for each surface. The shape and magnitude of posterior surface curvature obtained from OCT was similar to topography. The same analysis performed using cubic spline yielded noise in the curvature analysis probably due to errors associated with manual segmentation.
This study presents a feasible method of analyzing graft-host interface and posterior graft surface curvatures after DSAEK.
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