3-D characterization of the corneal shape in Fuchs dystrophy and pseudophakic keratopathy.

PURPOSE: To characterize the 3-D corneal shape deformation incurred by Fuchs corneal dystrophy and pseudophakic bullous keratopathy by using the integrated analysis of Orbscan (Bausch & Lomb Surgical, Rochester, NY) topographic maps of affected and normal corneas. METHODS: One hundred thirty-seven patients with Fuchs dystrophy or pseudophakic keratopathy were divided into three groups according to the severity of the disease: mild (central corneal thickness [CCT], 500-710 µm; n = 46); moderate (710-775 µm; n = 45), and severe (775-1100 µm; n = 46). A control group included 411 normal subjects matched for age and refractive spherical equivalent (three control subjects for each subject with Fuchs or pseudophakic keratopathy). The four groups were compared by using 3-D corneal shape atlases illustrating mean anterior elevation, posterior elevation, and pachymetry. RESULTS: Whereas the atlases showed little anterior surface deformation, the posterior surface presented a significant central bulging toward the anterior chamber. The thinnest point was displaced away from the center, toward the superior nasal midperiphery. The corneal periphery remained relatively unaffected by the disease, except in the final stage. CONCLUSIONS: 3-D atlases provided detailed new information on the 3-D corneal shape deformation incurred by Fuchs corneal dystrophy throughout disease progression.

Optical coherence tomography anatomy of the corneal endothelial transplantation wound.

PURPOSE: The goal of this study was to prospectively assess the deep lamellar endothelial keratoplasty (DLEK) wound anatomy and its evolution during the 12 months after surgery, using optical coherence tomography (OCT). METHODS: The eyes of 8 patients (1 eye per patient) who consecutively underwent DLEK for Fuchs dystrophy or pseudophakic bullous keratopathy were prospectively studied before and 1, 3, 6, and 12 months after surgery. The Stratus OCT apparatus (Carl Zeiss Meditec, Dublin, CA) was used to acquire central and radial scans perpendicular to the wound at 3-, 6-, 9-, and 12-o'clock positions. The following parameters were analyzed: central total thickness, posterior donor-recipient edges gap, donor-recipient height mismatch, tissue compression, and graft detachment. RESULTS: A posterior gap was observed in 4 of the 8 DLEK eyes. At 12 months, the mean gap contour, depth, and width were 242 +/- 67, 101 +/- 45, and 87 +/- 29 microm, respectively. A step was documented in all DLEK eyes (average step height 108 +/- 24 microm). A micrograft detachment was observed in one case and tissue compression in another. In all corneas, the mean central corneal thickness returned to normal range and almost normal anatomy with time after surgery. CONCLUSIONS: OCT was found to be a very useful tool for DLEK corneal wound architecture analysis. It revealed microscopic wound irregularities and allowed their quantitative follow-up with time.

Three-dimensional trajectory assessment of an IVUS transducer from single-plane cineangiograms: a phantom study.

The recovery of the three-dimensional (3-D) path of the transducer used during an intravascular ultrasound (IVUS) examination is of primary importance to assess the exact 3-D shape of the vessel under study. Traditionally, the reconstruction is done by simply stacking the images during the pullback, or more recently using biplane angiography to recover the vessel curvature. In this paper, we explain, how single-plane angiography can be used with two projection models, to perform this task. Two types of projection geometry are analyzed: weak-perspective and full-perspective. In weak-perspective projection geometry, the catheter path can be reconstructed without prior transducer depth information. With full-perspective projection geometry, precise depth location of reference points are needed in order to minimize the error of the recovered transducer angle of incidence. The transducer angulation reconstruction is based on the foreshortening effect as seen from the X-ray images. By comparing the measured to the true transducer length, we are able to get its incidence angle. The transducer trajectory is reconstructed by stitching together the different estimated angulations obtained from each image in a cineangiogram sequence. The method is described and validated on two helical vessel phantoms, giving on average a reconstructed path that is less than 2 mm distant from the true path when using full-perspective projection.