Purpose: To determine directional changes in peripheral corneal thickness and corneal astigmatism over a range of severity of Fuchs' endothelial corneal dystrophy (FECD).
Methods: Eyes with FECD were categorized as mild, moderate, or advanced according to the area and confluence of guttae and the presence of clinical edema. Normal corneas were devoid of guttae. Peripheral thickness centered on the corneal apex, and radii of posterior curvature were measured with Scheimpflug imaging. Variables were compared between groups by using generalized estimating equation models.
Results: Scheimpflug images were acquired in 101 normal corneas and 112 corneas with FECD. Normal corneas were 8.6 ± 4.8 μm thicker vertically than horizontally (P = 0.001); the steep posterior meridian was vertical in 91% of corneas. The difference between vertical and horizontal thicknesses decreased to 4.7 ± 7.3 μm in advanced FECD (P = 0.008); 46% had a steep vertical posterior meridian (P = 0.001). Vertical radius of curvature was flatter than normal in moderate (by 0.2 mm, P = 0.011) and advanced (by 0.4 mm, P < 0.001) FECD. Mean posterior corneal power was less negative in moderate (by 0.2 diopters [D], P = 0.009) and advanced (by 0.4 D, P < 0.001) FECD compared to normal.
Conclusions: Posterior toricity is abnormal in advanced FECD because of relatively greater horizontal than vertical corneal thickening. Posterior corneal power decreases (i.e., is less negative) in moderate and advanced FECD, which can affect the choice of intraocular lens power during cataract surgery, and might explain the hyperopic shift after Descemet membrane endothelial keratoplasty.