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Cherie B. Nau, Jay W. McLaren, Keith H. Baratz, Sanjay V. Patel; Graft Microfolds, Graft Thickness, and Ocular Aberrations after Descemet-Stripping Endothelial Keratoplasty for Fuchs Endothelial Dystrophy. Invest. Ophthalmol. Vis. Sci. 2011;52(14):778.
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© ARVO (1962-2015); The Authors (2016-present)
Visual acuity often remains less than 20/20 after Descemet-stripping endothelial keratoplasty (DSEK), possibly because of aberrations induced by an irregular posterior graft surface. Confocal images of DSEK grafts often show stromal microfolds. In this study we examined the relationships between graft microfolds, graft thickness, and aberrations after DSEK.
Twenty-three corneas of 17 patients at 2 years after DSEK for Fuchs dystrophy, and 36 corneas of 18 normal untreated subjects, were examined by using a ConfoScan 4 confocal microscope with the z-ring adapter. Central graft microfolds, which appeared as dark striations, were counted in a standard area of each image in the donor tissue. The total number of folds (sum of the number of folds per frame weighted for the distance between consecutive frames) was calculated between the interface and the endothelium after DSEK, or between the endothelium and 160 µm anterior to the endothelium in untreated corneas. Central graft thickness was the distance between images of the interface and endothelium in eyes after DSEK. Wavefront aberrations were determined from Hartmann-shack aberrometry over a 4 mm optical zone, and best-corrected visual acuity (BCVA) was measured by using the ETDRS protocol. Correlations between visual parameters, the total number of microfolds, and graft thickness, were assessed by using generalized estimating equation models.
After DSEK, the total number of microfolds was correlated with total high-order aberrations (HOAs, r=0.52, p<0.001), trefoil (r=0.65, p<0.001) and graft thickness (r=0.43, p=0.01). Graft thickness was also correlated with total HOAs (r=0.76, p<0.001), coma (r=0.58, p<0.001), and trefoil (r=0.79, p<0.001). BCVA after DSEK was weakly correlated with trefoil (r=0.22, p=0.04). The total number of microfolds in DSEK grafts (350 ±137 folds-µm) was higher than in normal corneas (200 ± 144 folds-µm, p<0.001). In normal corneas, posterior stromal microfolds were not correlated with total HOAs (r= -0.19, p=0.17) or with BCVA (r= -0.10, p=0.29).
Although increased HOAs after DSEK are associated with an increased number of graft microfolds and thicker grafts, there is a weak association between HOAs and BCVA. Microfolds also appear in normal corneas, and might be an artifact of pressure exerted by the z-ring during confocal microscopy. Nevertheless, in normal corneas, there were fewer microfolds than in DSEK grafts, and microfolds were not associated with HOAs.
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