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Effect of the shape of the endothelial graft on the refractive results after Descemet's stripping with automated endothelial keratoplasty.

OBJECTIVE
To investigate the magnitude and the possible causes of the refractive changes after Descemet's stripping with automated endothelial keratoplasty (DSAEK). In this article we describe the changes in corneal power after DSAEK and correlate them with the shape, diameter, and thickness of the endothelial graft obtained.


STUDY DESIGN
Retrospective chart review.


PARTICIPANTS
17 consecutive patients who underwent DSAEK at the Rand Eye Institute in 2007.


METHODS
The preoperative and post-DSAEK corneal power was determined using Gaussian optics and correlated with the DSAEK graft diameter and central, paracentral (P1), and peripheral (P2) graft thickness using images obtained from the Pentacam Scheimpflug.


RESULTS
During DSAEK there is addition of corneal tissue in the posterior layers of the cornea, which reduces the radius of curvature of the posterior layer of the cornea and also the total corneal power. The mean anterior:posterior corneal radius of curvature ratio after DSAEK is 72.3% (SD 4.63%). In consequence, the keratometry values calculated after DSAEK using the Gaussian optics method are less than those measured by manual keratometry after surgery. A strong correlation was observed between the postoperative Gaussian keratometric power and the ratio of the central corneal DSAEK graft thickness (C) to the mean P2 measured at 7 mm optical zone (C:P2) (r2 = 0.63, p< 0.01).


CONCLUSIONS
DSAEK induced a mean hyperopic shift of 1.05 (SD 0.76) D. The mean anterior:posterior corneal radius of curvature ratio decreased to 72.3%. Despite a great variability, the ratio between the central DSAEK graft thickness and the graft thickness at the 7 mm optical zone (C:P2 ratio) was correlated with the magnitude of the change in corneal power and induced hyperopia, which produces a steeper posterior corneal surface. No correlation between the DSAEK graft diameter and change in corneal power was noted. Customization in the shape of the donor graft lenticle might reduce the hyperopic shift noted after DSAEK.