Does CXL at the slit lamp affect demarcation line depth?

The advantages of performing corneal cross-linking (CXL) at the slit lamp are well established. It brings CXL out of the operating theater, to anywhere where there is a slit lamp – a procedure room, or the doctor’s office. This saves time and money, and simplifies the procedure for doctor and patient alike. The fact that CXL also kills pathogens also means that the cornea is effectively sterile once the procedure is complete.

Several questions have been asked regarding CXL being performed in the sitting position, as opposed to the lying position. Does the gravity of sitting upright affect riboflavin distribution? The answer is “no”, we published this study in 2017 already.

Might it affect how deep the strengthening effect of CXL is in the cornea? In principle, it should not – the interaction between riboflavin, corneal tissue and the photons of UV light should not be affected by a person sitting up or lying down. But would this assumption hold true when it was tested in the clinical setting?

To do this, Prof. Hafezi, Medical Director of the ELZA Institute, and his team decided to compare a marker of how deep the cross-linking effect is (called the “demarcation line”) in 23 patients who had undergone CXL at the slit lamp for progressive keratoconus (n=22) or post-LASIK ectasia (n=1), with previously published demarcation line depths. What did they find?

They found that the demarcation line depth was similar in both groups. As would be expected, sitting upright for CXL, instead of lying supine makes no difference to the depth of the cross-linking effect.

Click on the image to download the paper.

demarcation line depth paper


Hafezi, F.; Lu, N.-J.; Assaf, J.F.; Hafezi, N.L.; Koppen, C.; Vinciguerra, R.; Vinciguerra, P.; Hillen, M.; Awwad, S.T. Demarcation Line Depth in Epithelium-Off Corneal Cross-Linking Performed at the Slit Lamp. J. Clin. Med. 2022, 11, 5873.


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