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Corneal Collagen Cross-linking Combined With Simulation of Femtosecond Laser–Assisted Refractive Lens Extraction

An Ex Vivo Biomechanical Effect Evaluation

Kanellopoulos, Anastasios J. MD; Kontos, Mark A. MD; Chen, Shihao MD, OD, MSc; Asimellis, George PhD

doi: 10.1097/ICO.0000000000000376
Basic Investigation

Purpose: To evaluate biomechanical changes induced by in situ corneal cross-linking (CXL) with stromal pocket delivered enhanced concentration riboflavin and high-fluence, high-energy UV-A irradiation.

Methods: Eight human donor corneas were subjected to intrastromal lamellar corneal tissue removal of anterior 140-μm deep, 80-μm thick × 5-mm diameter central stromal buttons, extracted through a 3.5-mm width tunnel, surfacing in the superior cornea periphery. Enhanced concentration riboflavin solution (0.25%) was instilled in the pocket. In study group A (CXL), superficial high-fluence UV-A irradiation was applied, whereas in control group B (no CXL), none. To comparatively assess changes in corneal rigidity, corneal specimens were subjected to transverse biaxial resistance measurements by application of a unidirectional tangential shear force. Biomechanical differences were evaluated through stress and Young shear modulus.

Results: Stress at 10% strain was 305 ± 24 kPa in study group A versus 157 ± 11 kPa in control group B (relative difference Δ = 107%, P = 0.021). Stress at 20% strain was 1284 ± 34 kPa in study group A versus 874 ± 29 kPa in control group B (Δ = 47%, P = 0.043). Average shear modulus in study group A at 10% strain was 6.98 ± 1.12 MPa versus 4.04 ± 0.85 MPa in control group B (Δ = 73%, P = 0.036). Average shear modulus in study group A at 20% strain was 11.46 ± 0.75 MPa versus 8.80 ± 0.72 MPa in group B (Δ = 30%, P = 0.047).

Conclusions: Adjunct CXL in this ex vivo simulation refractive lens extraction procedure seems to provide significant increase in corneal rigidity, up to +107%. These findings also support our previous reported work on laser in situ keratomileusis combined with CXL.

* Clinical and Research Eye Institute, Eye Institute, Athens, Greece;

New York University Medical School, New York, NY;

Empire Eye Physicians, Spokane, WA; and

§Affiliated Eye Hospital of Wenzhou Medical University, Zhejiang, China.

Reprints: Anastasios J. Kanellopoulos, MD, Clinical and Research Eye Institute, Eye Institute, 17 Tsocha St, Athens 11521, Greece (e-mail:

A. J. Kanellopoulos holds consultant/advisory positions in Alcon/WaveLight, Avedro, i-Optics, and Oculus and M. A. Kontos in Abbott Medical. The remaining authors have no funding or conflicts of interest to disclose.

Received November 04, 2014

Received in revised form December 15, 2014

Accepted December 18, 2014

Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.