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Scheimpflug Imaging of Corneas After Collagen Cross-Linking

Koller, Tobias MD; Iseli, Hans Peter MD; Hafezi, Farhad MD, PhD; Vinciguerra, Paolo MD; Seiler, Theo MD, PhD

doi: 10.1097/ICO.0b013e3181915943
Clinical Science

Purpose: To compare geometrical shape factors of keratoconus corneas after cross-linking (CXL) by means of Scheimpflug imaging with those of untreated fellow eyes.

Setting: Institut für Refraktive und Ophthalmo-Chirurgie, Zürich, Switzerland.

Methods: Scheimpflug imaging of the anterior segments was performed with the Pentacam (Oculus, Wetzlar, Germany) in 21 patients with progressive keratectasia before and after CXL. Only 1 eye per patient was treated with corneal cross-linking using the riboflavin/UV-A approach, the fellow eye serving as control. The following corneal parameters and their postoperative evolution during 1 year after treatment have been evaluated: minimal curvature radius and its location, thickness at the thinnest point, location of the thinnest point, anterior and posterior elevation, conoid asphericity constants of the anterior and posterior surface, and 7 keratoconus indices. Statistical comparison was performed by means of the Wilcoxon test.

Results: None of the treated eyes showed topographic progression in contrast to the untreated group where 8 eyes experienced significant progression. Minimal curvature radius increased significantly after 1 year compared with preoperative (6.14-6.21 mm), whereas in the untreated fellow eye, it significantly decreased (6.94-6.86 mm). Minimal corneal thickness was significantly reduced after treatment (P < 0.002 at 12 months). The cornea showed an evolution toward a more regular shape as indicated by a significant reduction in 4 of 7 keratoconus indices. No complications of CXL occurred in this small study group.

Conclusions: After cross-linking, the corneal shape undergoes a process of regularization. This process is active during the first year after treatment and may continue. Longer follow-up is warranted to estimate the full amount of regression of the keratectasia after CXL.

From the *Institut für Refraktive und Ophthalmo-Chirurgie, Zürich, Switzerland; and †Istitut Clinico Humanitas, Milano, Italy.

Received for publication May 28, 2008; revision received September 29, 2008; accepted October 12, 2008.

The authors have no financial interest in the devices and medications used in this study.

Reprints: Theo Seiler, MD, PhD, Institut für Refraktive und Ophthalmo-Chirurgie, Stockerstrasse 37, CH-8002 Zürich, Switzerland (e-mail:

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