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Corneal Cross-Linking-Induced Stromal Demarcation Line

Seiler, Theo MD, PhD; Hafezi, Farhad MD

doi: 10.1097/01.ico.0000225720.38748.58
Clinical Science

Purpose: Corneal collagen cross-linking by UVA/riboflavin (X-linking) represents a new method for the treatment of progressive keratoconus and currently is under clinical study. To avoid UVA irradiation damage to the corneal endothelium, the parameters for X-linking are set in a way that effective treatment occurs only in the first 300 μm of the corneal stroma. Here, X-linking not only strengthens the biomechanical properties of the cornea but also induces keratocyte apoptosis. To date, the effectiveness of treatment could be monitored only indirectly by postoperative follow-up corneal topographies or using corneal confocal microscopy. Here we describe a corneal stromal demarcation line indicating the transition zone between cross-linked anterior corneal stroma and untreated posterior corneal stroma. The demarcation line is biomicroscopically detectable in slit-lamp examination as early as 2 weeks after treatment.

Methods: X-linking was performed in 16 cases of progressive keratoconus, and corneas were examined biomicroscopically and by means of corneal topography and pachymetry before and after treatment.

Results: In 14 of 16 cases, a thin stromal demarcation line was visible at a depth of approximately 300 μm over the whole cornea after X-linking treatment.

Conclusion: This newly observed demarcation line may result from differences in the refractive index and/or reflection properties of untreated versus X-linked corneal stroma and represents an effective tool to biomicroscopically easily monitor the depth of effective X-linking treatment in keratoconus.

From the Institute for Refractive and Ophthalmic Surgery, Zurich, Switzerland.

Received for publication February 21, 2006; accepted April 26, 2006.

The authors state that they have no proprietary interest in the products named in this article.

Reprints: Farhad Hafezi, MD. IROC, Institute for Refractive and Ophthalmic Surgery, Stockerstrasse 37, CH-8002 Zurich, Switzerland (e-mail:

© 2006 Lippincott Williams & Wilkins, Inc.