COMPARING THE BIOMECHANICAL EFFECT AND DEMARCATION LINE DEPTH OF EPI-ON AND ACCELERATED EPI-OFF CXL PROTOCOLS
Published 2024 - 28th ESCRS Winter Meeting
Reference: FP53 | Type: Submission | DOI: 10.82333/s6xf-zk26
Authors: Farhad Hafezi* 1 , Nanji Lu 1 , Emilio A. Torres-Netto 1 , Enes Aydemir 1 , Sabine Kling 2 , Nikki Hafezi 3 , Mark Hillen 3
1Ophthalmology,ELZA Institute,Dietikon/Zurich,Switzerland;Laboratory for Ocular Cell Biology,University of Zurich,Zurich,Switzerland, 2Institute for Biomedical Engineering,ETH Zurich,Zurich,Switzerland, 3Ophthalmology,ELZA Institute,Dietikon/Zurich,Switzerland
Purpose
To compare the biomechanical effect of a novel epithelium-on (epi-on) corneal cross-linking (CXL) protocol without iontophoresis or additional oxygen to a commonly performed accelerated epithelium-off (epi-off) CXL protocol, and assess demarcation line depth in progressive keratoconus patients post-epi-on CXL.
Setting
Clinical: ELZA Institute, Zurich; Laboratory: CABMM, University of Zurich, Switzerland.
Methods
Experimentally, 150 porcine eyes were equally divided into epi-on, epi-off, and control groups. The epi-on group received 18 mW/cm² pulsed UV-A light for 15 min (fluence 8.1 J/cm²); the epi-off group received 9 mW/cm² continuous UV-A light for 10 min (fluence 5.4 J/cm²). Stress-strain extensiometry assessed corneal biomechanics. Clinically, 23 eyes from 19 keratoconus patients underwent the new epi-on CXL protocol. Demarcation line depth was assessed at one month post-treatment using high-resolution anterior segment OCT imaging.
Results
Experimentally: the mean elastic modulus between 5% and 10% of strain was 5.21 ± 1.58 N/mm in epi-on, 4.95 ± 1.50 N/mm in epi-off, and 4.01 ± 1.41 N/mm in controls. No significant differences in elastic modulus between epi-on and epi-off groups (P=0.45), but significant differences versus controls (P<0.001 and P=0.001, respectively). Clinically: the mean epi-on demarcation line depth was 225 µm ± 34 µm (range 148 µm – 274 µm).
Conclusion
This epi-on CXL protocol provided biomechanical stiffening similar to the epi-off CXL protocol without iontophoresis or additional oxygen, and clinical evaluation revealed comparable demarcation line depths to the accelerated epi-on protocol. This simple protocol can be performed at the slit lamp and may avoid several drawbacks associated with epi-off CXL.