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Corneal cross-linking (CXL) in ultrathin corneas: individualizing UV irradiation times

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Session Details

Session Title: Cross-Linking

Session Date/Time: Tuesday 10/10/2017 | 14:00-16:30

Paper Time: 16:08

Venue: Room 4.6

First Author: : S.Kling SWITZERLAND

Co Author(s): :    E. Torres Netto   F. Hafezi                 

Abstract Details


Corneal cross-linking (CXL) is effective in preventing the progression of keratoconus. To date, CXL treatment is only recommended for corneas thicker than 400 μm at the time of UV irradiation, preventing its application in advanced stages of keratoconus. We have recently developed a theoretical model that allows to predict the depth of corneal stiffening and to customize CXL treatment settings. In the current study, the model predictions were validated in a clinical setting.


Prospective clinical and experimental study; ELZA Institute AG, Dietikon/Zurich, Switzerland; Laboratory of Ocular Cell Biology, CABMM, University of Zurich, Switzerland.


27 eyes of 27 keratoconus patients scheduled for CXL treatment were included in this study. All corneas had a thickness of lower than 400 μm after epithelial abrasion and 0.1% hypoosmolar riboflavin instillation for 20 min. Per the model predictions, the standard UV irradiation time at an irradiance of 3 mW/cm2 was shortened to a range of 7 to 25 min to reach an effective depth of CXL up to 70μm distance to the endothelium. At 1 month post-CXL, the maximal depth of demarcation line was assessed by OCT and compared against the model predictions.


The achieved demarcation line depths ranged between 168 and 385μm. Demarcation line depth and central stromal thickness showed a positive correlation (coeffpearson= 0.79) with a gradient of 1.93 μmdemarcation_depth/μmstroma (R2= 0.63). The theoretically predicted logarithmic relation between UV irradiation time and effective depth of cross-linking was confirmed (R2= 0.55). Surprisingly, a strong negative correlation (coeffpearson= -0.93) was observed between the anterior and posterior distance to the demarcation line (R2= 0.86).


Shortening UV irradiation time allows CXL treatment in corneas thinner than the current limit of 400 μm. While a lower fluence reduces the risk of endothelial damage in thin corneas, the demarcation line depth seems not only to depend on irradiation time, but also on the overall corneal thickness. These clinical observations will be used to further optimize the current model predictions.

Financial Disclosure:


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